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Logical Volume Manager Administration

Red Hat Enterprise Linux 6

LVM Administrator Guide

Steven Levine

Red Hat Customer Content Services

摘要

This book describes the LVM logical volume manager, including information on running LVM in a clustered environment.

第 1 章 简介
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This book describes the Logical Volume Manager (LVM), including information on running LVM in a clustered environment.

1.1. 读者
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This book is intended to be used by system administrators managing systems running the Linux operating system. It requires familiarity with Red Hat Enterprise Linux 6.

1.2. 软件版本
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Expand
表 1.1. 软件版本
软件描述
Red Hat Enterprise Linux 6
refers to Red Hat Enterprise Linux 6 and higher
GFS2
refers to GFS2 for Red Hat Enterprise Linux 6 and higher

1.4. We Need Feedback!
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If you find a typographical error in this manual, or if you have thought of a way to make this manual better, we would love to hear from you! Please submit a report in Bugzilla: http://bugzilla.redhat.com/ against the product Red Hat Enterprise Linux 6 and the component doc-Logical_Volume_Manager. When submitting a bug report, be sure to mention the manual's identifier: 
Logical_Volume_Manager_Administration(EN)-6 (2017-3-8-15:20)
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If you have a suggestion for improving the documentation, try to be as specific as possible when describing it. If you have found an error, include the section number and some of the surrounding text so we can find it easily.

第 2 章 LVM 逻辑卷管理器
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This chapter provides a summary of the features of the LVM logical volume manager that are new for the initial and subsequent releases of Red Hat Enterprise Linux 6. Following that, this chapter provides a high-level overview of the components of the Logical Volume Manager (LVM).

2.1. New and Changed Features
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This section lists new and changed features of the LVM logical volume manager that are included with the initial and subsequent releases of Red Hat Enterprise Linux 6.
Red Hat Enterprise Linux 6.0 includes the following documentation and feature updates and changes.
  • You can define how a mirrored logical volume behaves in the event of a device failure with the mirror_image_fault_policy and mirror_log_fault_policy parameters in the activation section of the lvm.conf file. When this parameter is set to remove, the system attempts to remove the faulty device and run without it. When this parameter is set to allocate, the system attempts to remove the faulty device and tries to allocate space on a new device to be a replacement for the failed device; this policy acts like the remove policy if no suitable device and space can be allocated for the replacement. For information on the LVM mirror failure policies, see 第 5.4.3.1 节 “Mirrored Logical Volume Failure Policy”.
  • For the Red Hat Enterprise Linux 6 release, the Linux I/O stack has been enhanced to process vendor-provided I/O limit information. This allows storage management tools, including LVM, to optimize data placement and access. This support can be disabled by changing the default values of data_alignment_detection and data_alignment_offset_detection in the lvm.conf file, although disabling this support is not recommended.
    For information on data alignment in LVM as well as information on changing the default values of data_alignment_detection and data_alignment_offset_detection, see the inline documentation for the /etc/lvm/lvm.conf file, which is also documented in 附录 B, LVM 配置文件. For general information on support for the I/O Stack and I/O limits in Red Hat Enterprise Linux 6, see the Storage Administration Guide.
  • In Red Hat Enterprise Linux 6, the Device Mapper provides direct support for udev integration. This synchronizes the Device Mapper with all udev processing related to Device Mapper devices, including LVM devices. For information on Device Mapper support for the udev device manager, see 第 A.3 节 “Device Mapper Support for the udev Device Manager”.
  • For the Red Hat Enterprise Linux 6 release, you can use the lvconvert --repair command to repair a mirror after disk failure. This brings the mirror back into a consistent state. For information on the lvconvert --repair command, see 第 5.4.3.3 节 “Repairing a Mirrored Logical Device”.
  • As of the Red Hat Enterprise Linux 6 release, you can use the --merge option of the lvconvert command to merge a snapshot into its origin volume. For information on merging snapshots, see 第 5.4.8 节 “Merging Snapshot Volumes”.
  • As of the Red Hat Enterprise Linux 6 release, you can use the --splitmirrors argument of the lvconvert command to split off a redundant image of a mirrored logical volume to form a new logical volume. For information on using this option, see 第 5.4.3.2 节 “Splitting Off a Redundant Image of a Mirrored Logical Volume”.
  • You can now create a mirror log for a mirrored logical device that is itself mirrored by using the --mirrorlog mirrored argument of the lvcreate command when creating a mirrored logical device. For information on using this option, see 第 5.4.3 节 “创建镜像卷”.
Red Hat Enterprise Linux 6.1 includes the following documentation and feature updates and changes.
  • The Red Hat Enterprise Linux 6.1 release supports the creation of snapshot logical volumes of mirrored logical volumes. You create a snapshot of a mirrored volume just as you would create a snapshot of a linear or striped logical volume. For information on creating snapshot volumes, see 第 5.4.5 节 “创建快照卷”.
  • When extending an LVM volume, you can now use the --alloc cling option of the lvextend command to specify the cling allocation policy. This policy will choose space on the same physical volumes as the last segment of the existing logical volume. If there is insufficient space on the physical volumes and a list of tags is defined in the lvm.conf file, LVM will check whether any of the tags are attached to the physical volumes and seek to match those physical volume tags between existing extents and new extents.
    For information on extending LVM mirrored volumes with the --alloc cling option of the lvextend command, see 第 5.4.14.3 节 “Extending a Logical Volume with the cling Allocation Policy”.
  • You can now specify multiple --addtag and --deltag arguments within a single pvchange, vgchange, or lvchange command. For information on adding and removing object tags, see 第 D.1 节 “添加和删除对象标签”.
  • The list of allowed characters in LVM object tags has been extended, and tags can contain the "/", "=", "!", ":", "#", and "&" characters. For information on LVM object tags, see 附录 D, LVM 对象标签.
  • You can now combine RAID0 (striping) and RAID1 (mirroring) in a single logical volume. Creating a logical volume while simultaneously specifying the number of mirrors (--mirrors X) and the number of stripes (--stripes Y) results in a mirror device whose constituent devices are striped. For information on creating mirrored logical volumes, see 第 5.4.3 节 “创建镜像卷”.
  • As of the Red Hat Enterprise Linux 6.1 release, if you need to create a consistent backup of data on a clustered logical volume you can activate the volume exclusively and then create the snapshot. For information on activating logical volumes exclusively on one node, see 第 5.7 节 “在群集的独立节点中激活逻辑卷”.
Red Hat Enterprise Linux 6.2 includes the following documentation and feature updates and changes.
  • The Red Hat Enterprise Linux 6.2 release supports the issue_discards parameter in the lvm.conf configuration file. When this parameter is set, LVM will issue discards to a logical volume's underlying physical volumes when the logical volume is no longer using the space on the physical volumes. For information on this parameter, see the inline documentation for the /etc/lvm/lvm.conf file, which is also documented in 附录 B, LVM 配置文件.
Red Hat Enterprise Linux 6.3 includes the following documentation and feature updates and changes.
  • As of the Red Hat Enterprise Linux 6.3 release, LVM supports RAID4/5/6 and a new implementation of mirroring. For information on RAID logical volumes, see 第 5.4.16 节 “RAID Logical Volumes”.
  • When you are creating a new mirror that does not need to be revived, you can specify the --nosync argument to indicate that an initial synchronization from the first device is not required. For information on creating mirrored volumes, see 第 5.4.3 节 “创建镜像卷”.
  • This manual now documents the snapshot autoextend feature. For information on creating snapshot volumes, see 第 5.4.5 节 “创建快照卷”.
Red Hat Enterprise Linux 6.4 includes the following documentation and feature updates and changes.
  • Logical volumes can now be thinly provisioned. This allows you to create logical volumes that are larger than the available extents. Using thin provisioning, you can manage a storage pool of free space, known as a thin pool, to be allocated to an arbitrary number of devices when needed by applications. You can then create devices that can be bound to the thin pool for later allocation when an application actually writes to the logical volume. The thin pool can be expanded dynamically when needed for cost-effective allocation of storage space.
    For general information on thinly-provisioned logical volumes, see 第 3.3.5 节 “Thinly-Provisioned Logical Volumes (Thin Volumes)”. For information on creating thin volumes, see 第 5.4.4 节 “Creating Thinly-Provisioned Logical Volumes”.
  • The Red Hat Enterprise Linux release 6.4 version of LVM provides support for thinly-provisioned snapshot volumes. Thin snapshot volumes allow many virtual devices to be stored on the same data volume. This simplifies administration and allows for the sharing of data between snapshot volumes.
    For general information on thinly-provisioned snapshot volumes, see 第 3.3.7 节 “Thinly-Provisioned Snapshot Volumes”. For information on creating thin snapshot volumes, see 第 5.4.6 节 “Creating Thinly-Provisioned Snapshot Volumes”.
  • This document includes a new section detailing LVM allocation policy, 第 5.3.2 节 “LVM Allocation”.
  • LVM now provides support for raid10 logical volumes. For information on RAID logical volumes, see 第 5.4.16 节 “RAID Logical Volumes”.
  • The LVM metadata daemon, lvmetad, is supported in Red Hat Enterprise Linux release 6.4. Enabling this daemon reduces the amount of scanning on systems with many block devices. The lvmetad daemon is not currently supported across the nodes of a cluster, and requires that the locking type be local file-based locking.
    For information on the metadata daemon, see 第 4.6 节 “The Metadata Daemon (lvmetad)”.
In addition, small technical corrections and clarifications have been made throughout the document.
Red Hat Enterprise Linux 6.5 includes the following documentation and feature updates and changes.
In addition, small technical corrections and clarifications have been made throughout the document.
Red Hat Enterprise Linux 6.6 includes the following documentation and feature updates and changes.
In addition, small technical corrections and clarifications have been made throughout the document.
Red Hat Enterprise Linux 6.7 includes the following documentation and feature updates and changes.
Red Hat Enterprise Linux 6.8 includes the following documentation and feature updates and changes.
  • When defining selection criteria for LVM commands, you can now specify time values as selection criteria for fields with a field type of time. For information on specifying time values as selection criteria, see 第 C.3.1 节 “Specifying Time Values”.

2.2. 逻辑卷
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Volume management creates a layer of abstraction over physical storage, allowing you to create logical storage volumes. This provides much greater flexibility in a number of ways than using physical storage directly. With a logical volume, you are not restricted to physical disk sizes. In addition, the hardware storage configuration is hidden from the software so it can be resized and moved without stopping applications or unmounting file systems. This can reduce operational costs.
逻辑卷在直接使用物理存储时有以下优势：
  • 灵活的容量
    当使用逻辑卷时，可在多个磁盘间扩展文件系统，因为您可以将磁盘和分区集合成一个逻辑卷。
  • 重新设定存储池大小
    您可以使用检单的软件命令增大或者减小逻辑卷的大小，而无需对所在磁盘设备重新格式化或者重新分区。
  • 在线数据重新定位
    要部署更新、更快或者更有弹性的存储子系统，以便您可以在系统活跃时移动数据。数据可以在磁盘正在使用时进行重新分配。例如，您可以在删除一个热交换磁盘之前将其清空。
  • 方便设备命名
    逻辑存储卷可在用户定义的组群中进行管理，这些组群可按您的要求进行命名。
  • 磁盘条带
    您可以创建一个可在两个或者更多磁盘间条状分布数据的逻辑卷。这可大幅度提高吞吐量。
  • 镜像卷
    逻辑卷为您提供了一个方便配置数据镜像的方法。
  • 卷快照
    使用逻辑卷，您可以提取设备快照，这样可在持续备份或者在不影响真实数据的情况下测试修改效果。
本文档的以下内容对在 LVM 中实施这些特性进行了论述。

2.3. LVM 构架总览
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For the Red Hat Enterprise Linux 4 release of the Linux operating system, the original LVM1 logical volume manager was replaced by LVM2, which has a more generic kernel framework than LVM1. LVM2 provides the following improvements over LVM1:
  • 灵活的容量
  • 更有效的元数据存储
  • 更好的修复格式
  • 新的 ASCII 元数据格式
  • 元数据微调
  • 元数据冗余副本
LVM2 可向下兼容 LVM1，但不支持 LVM1 的快照和群集。您可以使用 vgconvert 命令将卷组从 LVM1 格式转换成 LVM2 格式。有关转换 LVM 元数据格式的详情请参考 vgconvert(8) man page。
LVM 逻辑卷的基本物理存储单元是块设备，比如分区或者整个磁盘。这个设备是作为 LVM 物理卷（PV）进行初始化的。
要创建一个 LVM 逻辑卷，就要将物理卷合并到卷组（VG）中。这就生成了磁盘空间池，用它可分配 LVM 逻辑卷（LV）。这个过程和将磁盘分区的过程类似。逻辑卷由文件系统和应用程序（比如数据库）使用。
图 2.1 “LVM Logical Volume Components” shows the components of a simple LVM logical volume:
LVM Logical Volume Components
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LVM Logical Volume Components

图 2.1. LVM Logical Volume Components

For detailed information on the components of an LVM logical volume, see 第 3 章 LVM 组成.

2.4. 群集逻辑卷管理器（CLVM）
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The Clustered Logical Volume Manager (CLVM) is a set of clustering extensions to LVM. These extensions allow a cluster of computers to manage shared storage (for example, on a SAN) using LVM. CLVM is part of the Resilient Storage Add-On.
您是否应该使用 CLVM 取决于您的系统要求：
  • 如果您的系统中只有一个节点需要访问您正在将其配置为逻辑卷的存储，那么您可以使用 LVM 而不是 LVM 扩展，且在该节点中生成的逻辑卷对该节点来说都是本地的。
  • If you are using a clustered system for failover where only a single node that accesses the storage is active at any one time, you should use High Availability Logical Volume Management agents (HA-LVM).
  • 如果您的群集中有一个以上的节点需要访问您的存储，那么该存储会在所有活跃的节点间共享，则您必须使用 CLVM。CLVM 允许用户通过在配置逻辑卷时锁定对物理存储的访问来在共享存储中配置逻辑卷，并使用群集的锁定服务管理共享存储。
In order to use CLVM, the High Availability Add-On and Resilient Storage Add-On software, including the clvmd daemon, must be running. The clvmd daemon is the key clustering extension to LVM. The clvmd daemon runs in each cluster computer and distributes LVM metadata updates in a cluster, presenting each cluster computer with the same view of the logical volumes. For information on installing and administering the High Availability Add-On see Cluster Administration.
To ensure that clvmd is started at boot time, you can execute a chkconfig ... on command on the clvmd service, as follows: 
# chkconfig clvmd on
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如果还没有启动 clvmd 守护进程，您可以对 clvmd 服务执行 service ... start 命令，如下： 
# service clvmd start
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Creating LVM logical volumes in a cluster environment is identical to creating LVM logical volumes on a single node. There is no difference in the LVM commands themselves, or in the LVM graphical user interface, as described in 第 5 章 用 CLI 命令管理 LVM and 第 8 章 用 LVM GUI 进行 LVM 管理. In order to enable the LVM volumes you are creating in a cluster, the cluster infrastructure must be running and the cluster must be quorate.
By default, logical volumes created with CLVM on shared storage are visible to all systems that have access to the shared storage. It is possible to create volume groups in which all of the storage devices are visible to only one node in the cluster. It is also possible to change the status of a volume group from a local volume group to a clustered volume group. For information, see 第 5.3.3 节 “在群集中创建卷组” and 第 5.3.8 节 “修改卷组参数”.

警告

When you create volume groups with CLVM on shared storage, you must ensure that all nodes in the cluster have access to the physical volumes that constitute the volume group. Asymmetric cluster configurations in which some nodes have access to the storage and others do not are not supported.
图 2.2 “CLVM 总览” shows a CLVM overview in a cluster.
CLVM 总览
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CLVM 总览

图 2.2. CLVM 总览

注意

CLVM requires changes to the lvm.conf file for cluster-wide locking. Information on configuring the lvm.conf file to support clustered locking is provided within the lvm.conf file itself. For information about the lvm.conf file, see 附录 B, LVM 配置文件.

2.5. 文档总览
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本文档还包含以下章节：

第 3 章 LVM 组成
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本章论述了 LVM 逻辑卷的组成。

3.1. 物理卷
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LVM 逻辑卷的基本物理存储单元是块设备，比如分区或者整个磁盘。这个设备是作为 LVM 物理卷（PV）进行初始化的。将块设备作为物理卷进行初始化会在接近设备起始处放置一个标签。
默认情况下，LVM 标签是放在第二个 512 字节扇区。您可以将标签放在最开始的四个扇区之一来覆盖这个默认设置。这样就允许在必要时 LVM 卷可与其它使用这些扇区的用户共同存在。
LVM 标签可为物理设备提供正确的识别和设备排序，因为在引导系统时，设备可以任何顺序出现。LVM 标记在重新引导和整个群集中保持不变。
LVM 标记可识别作为 LVM 物理卷的设备。它为物理卷包含一个随机特定识别符号（UUID）。它还用字节记录块设备的大小，并记录 LVM 元数据在设备中的存储位置。
LVM 元数据包含您的系统中 LVM 卷组的配置详情。在默认情况下，在卷组中的每个物理卷中都会在其元数据区域保留一个一样的副本。LVM 元数据很小，并可以 ASCII 格式保存。
现在，LVM 允许您在每个物理卷中保存 0、1 或者 2 个元数据副本。默认是保存一个副本。一旦您设置了在物理卷中保存的元数据备份数目之后就无法再更改了。第一个副本保存在设备的起始位置，紧挨着标签。如果有第二个副本，会将其放在设备的末尾。如果您不小心写入了不同于您想要写入的磁盘从而覆盖了磁盘的起始部分，那么您可以使用在设备末尾的元数据第二个副本可让进行恢复。
For detailed information about the LVM metadata and changing the metadata parameters, see 附录 E, LVM 卷组元数据.

3.1.1. LVM Physical Volume Layout
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图 3.1 “物理卷布局” shows the layout of an LVM physical volume. The LVM label is on the second sector, followed by the metadata area, followed by the usable space on the device.

注意

在 Linux 内核（在整个文档中），每个扇区的大小为 512K。
物理卷布局
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物理卷布局

图 3.1. 物理卷布局

3.1.2. 一个磁盘中有多个分区
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LVM 允许您在磁盘分区外创建物理卷。通常建议您创建可覆盖整个磁盘的单一分区，并将其标记为 LVM 物理卷，理由如下：
  • 方便管理
    如果每个正真的磁盘只出现一次会比较容易在系统中追踪硬件，这在磁盘失败时尤为突出。另外，单一磁盘中有多个物理卷可导致内核在引导时发出未知分区类型警告。
  • 条带性能
    LVM cannot tell that two physical volumes are on the same physical disk. If you create a striped logical volume when two physical volumes are on the same physical disk, the stripes could be on different partitions on the same disk. This would result in a decrease in performance rather than an increase.
Although it is not recommended, there may be specific circumstances when you will need to divide a disk into separate LVM physical volumes. For example, on a system with few disks it may be necessary to move data around partitions when you are migrating an existing system to LVM volumes. Additionally, if you have a very large disk and want to have more than one volume group for administrative purposes then it is necessary to partition the disk. If you do have a disk with more than one partition and both of those partitions are in the same volume group, take care to specify which partitions are to be included in a logical volume when creating striped volumes.

3.2. 卷组
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物理卷合并为卷组（VG）。这样就创建了一个磁盘空间池，在它之外可分配逻辑卷。
Within a volume group, the disk space available for allocation is divided into units of a fixed-size called extents. An extent is the smallest unit of space that can be allocated. Within a physical volume, extents are referred to as physical extents.
逻辑卷会被分配成与物理卷扩展相同大小的逻辑扩展。因此卷组中逻辑卷的扩展大小都是一样的。卷组将逻辑扩展与物理扩展匹配。

3.3. LVM 逻辑卷
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在 LVM 中，卷组会被分成逻辑卷。LVM 逻辑卷有三种类型：线性卷、条状卷和镜像卷。这些在以后的内容中都有论述。

3.3.1. 线性卷
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A linear volume aggregates space from one or more physical volumes into one logical volume. For example, if you have two 60GB disks, you can create a 120GB logical volume. The physical storage is concatenated.
Creating a linear volume assigns a range of physical extents to an area of a logical volume in order. For example, as shown in 图 3.2 “扩展映射” logical extents 1 to 99 could map to one physical volume and logical extents 100 to 198 could map to a second physical volume. From the point of view of the application, there is one device that is 198 extents in size.
扩展映射
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扩展映射

图 3.2. 扩展映射

The physical volumes that make up a logical volume do not have to be the same size. 图 3.3 “物理卷大小不同的线性卷” shows volume group VG1 with a physical extent size of 4MB. This volume group includes 2 physical volumes named PV1 and PV2. The physical volumes are divided into 4MB units, since that is the extent size. In this example, PV1 is 200 extents in size (800MB) and PV2 is 100 extents in size (400MB). You can create a linear volume any size between 1 and 300 extents (4MB to 1200MB). In this example, the linear volume named LV1 is 300 extents in size.
物理卷大小不同的线性卷
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物理卷大小不同的线性卷

图 3.3. 物理卷大小不同的线性卷

You can configure more than one linear logical volume of whatever size you require from the pool of physical extents. 图 3.4 “多逻辑卷” shows the same volume group as in 图 3.3 “物理卷大小不同的线性卷”, but in this case two logical volumes have been carved out of the volume group: LV1, which is 250 extents in size (1000MB) and LV2 which is 50 extents in size (200MB).
多逻辑卷
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多逻辑卷

图 3.4. 多逻辑卷

3.3.2. 条状逻辑卷
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当您向 LVM 逻辑卷写入数据时，文件系统在基本物理卷之间部署数据。您可以通过创建条状逻辑卷控制数据向物理卷写入的方法。对于大批量的读取和写入，这样可以提高数据输入/输出的效率。
Striping enhances performance by writing data to a predetermined number of physical volumes in round-robin fashion. With striping, I/O can be done in parallel. In some situations, this can result in near-linear performance gain for each additional physical volume in the stripe.
以下示例显示数据在三个物理卷之间进行条状分布。在这个图表中：
  • 数据的第一条写入 PV1
  • 数据的第二条写入 PV2
  • 数据的第三条写入 PV3
  • 数据的第四条写入 PV1
In a striped logical volume, the size of the stripe cannot exceed the size of an extent.
在三个 PV 中条状分配数据
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在三个 PV 中条状分配数据

图 3.5. 在三个 PV 中条状分配数据

Striped logical volumes can be extended by concatenating another set of devices onto the end of the first set. In order to extend a striped logical volume, however, there must be enough free space on the underlying physical volumes that make up the volume group to support the stripe. For example, if you have a two-way stripe that uses up an entire volume group, adding a single physical volume to the volume group will not enable you to extend the stripe. Instead, you must add at least two physical volumes to the volume group. For more information on extending a striped volume, see 第 5.4.14.1 节 “扩展条状卷”.

3.3.3. 镜像逻辑卷
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镜像维护不同设备中的相同的副本。当向一个设备中写入数据时，也会向第二个设备中写入，即镜像保存数据。这提供了在设备失败时的数据保护。当镜像的一个分支失败时，逻辑卷就成为一个线性卷，仍然可访问。
LVM 支持镜像卷。当您创建了一个镜像逻辑卷时，LVM 确定写入基本物理卷的数据被镜像保存到一个独立的物理卷中。使用 LVM，您可以创建有多个镜像的镜像逻辑卷。
LVM 镜像一般以 512KB 为单位分割要复制到区域中的设备。LVM 维护一个小的日志，可用来追踪哪些区域是和镜像同步的。默认情况下，该日志是保存在磁盘中的，这样可以使它在机器重启后得以保存，也可在内存中维护此日志。
图 3.6 “Mirrored Logical Volume” shows a mirrored logical volume with one mirror. In this configuration, the log is maintained on disk.
Mirrored Logical Volume
View larger image
Mirrored Logical Volume

图 3.6. Mirrored Logical Volume

For information on creating and modifying mirrors, see 第 5.4.3 节 “创建镜像卷”.

3.3.4. RAID Logical Volumes
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As of the Red Hat Enterprise Linux 6.3 release, LVM supports RAID logical volumes. For information on the RAID implementations that LVM supports, see 第 5.4.16 节 “RAID Logical Volumes”.

3.3.5. Thinly-Provisioned Logical Volumes (Thin Volumes)
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As of the Red Hat Enterprise Linux 6.4 release, logical volumes can be thinly provisioned. This allows you to create logical volumes that are larger than the available extents. Using thin provisioning, you can manage a storage pool of free space, known as a thin pool, which can be allocated to an arbitrary number of devices when needed by applications. You can then create devices that can be bound to the thin pool for later allocation when an application actually writes to the logical volume. The thin pool can be expanded dynamically when needed for cost-effective allocation of storage space.

注意

Thin volumes are not supported across the nodes in a cluster. The thin pool and all its thin volumes must be exclusively activated on only one cluster node.
By using thin provisioning, a storage administrator can over-commit the physical storage, often avoiding the need to purchase additional storage. For example, if ten users each request a 100GB file system for their application, the storage administrator can create what appears to be a 100GB file system for each user but which is backed by less actual storage that is used only when needed. When using thin provisioning, it is important that the storage administrator monitor the storage pool and add more capacity if it starts to become full.
To make sure that all available space can be used, LVM supports data discard. This allows for re-use of the space that was formerly used by a discarded file or other block range.
For information on creating thin volumes, see 第 5.4.4 节 “Creating Thinly-Provisioned Logical Volumes”.
Thin volumes provide support for a new implementation of copy-on-write (COW) snapshot logical volumes, which allow many virtual devices to share the same data in the thin pool. For information on thin snapshot volumes, see 第 3.3.7 节 “Thinly-Provisioned Snapshot Volumes”.

3.3.6. 快照卷
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LVM 的快照性能为您提供了在某个特定时刻，在不导致服务中断的情况下创建设备的虚拟映射可能性。在提取快照后，当对原始设备进行修改时，快照特性会和在修改前提取快照一样提供一个修改了的数据区域的副本，以便重建设备的状态。

注意

As of the Red Hat Enterprise Linux 6.4 release, LVM supports thinly-provisioned snapshots. For information on thinly provisioned snapshot volumes, see 第 3.3.7 节 “Thinly-Provisioned Snapshot Volumes”.

注意

LVM snapshots are not supported across the nodes in a cluster. You cannot create a snapshot volume in a clustered volume group.
Because a snapshot copies only the data areas that change after the snapshot is created, the snapshot feature requires a minimal amount of storage. For example, with a rarely updated origin, 3-5 % of the origin's capacity is sufficient to maintain the snapshot.

注意

文件系统的快照副本是虚拟副本，不是文件系统的真实介质备份。快照不是备份过程的替代行为。
The size of the snapshot governs the amount of space set aside for storing the changes to the origin volume. For example, if you made a snapshot and then completely overwrote the origin the snapshot would have to be at least as big as the origin volume to hold the changes. You need to dimension a snapshot according to the expected level of change. So for example a short-lived snapshot of a read-mostly volume, such as /usr, would need less space than a long-lived snapshot of a volume that sees a greater number of writes, such as /home.
If a snapshot runs full, the snapshot becomes invalid, since it can no longer track changes on the origin volume. You should regularly monitor the size of the snapshot. Snapshots are fully resizeable, however, so if you have the storage capacity you can increase the size of the snapshot volume to prevent it from getting dropped. Conversely, if you find that the snapshot volume is larger than you need, you can reduce the size of the volume to free up space that is needed by other logical volumes.
当您创建文件系统的快照时，仍可能对源系统有完全的读和写访问。如果快照中的一个块修改了，那么就会标记出那个块，并再不从原始卷中复制这个块。
快照特性有几个用途：
  • 最典型的就是，当您需要在逻辑卷中在不影响运行系统连续性的情况下执行备份操作时可提取一个快照，这样可以持续地更新数据。
  • 您可以在快照文件系统中执行 fsck 命令来检查文件系统的完整性，并确定源文件系统是否需要修复。
  • 因为快照是可读/写的，您可以通过获取快照并根据快照进行测试，来进行根据产品数据测试应用程序，而不会影响真实数据。
  • You can create LVM volumes for use with Red Hat virtualization. LVM snapshots can be used to create snapshots of virtual guest images. These snapshots can provide a convenient way to modify existing guests or create new guests with minimal additional storage. For information on creating LVM-based storage pools with Red Hat Virtualization, see the Virtualization Administration Guide.
For information on creating snapshot volumes, see 第 5.4.5 节 “创建快照卷”.
As of the Red Hat Enterprise Linux 6 release, you can use the --merge option of the lvconvert command to merge a snapshot into its origin volume. One use for this feature is to perform system rollback if you have lost data or files or otherwise need to restore your system to a previous state. After you merge the snapshot volume, the resulting logical volume will have the origin volume's name, minor number, and UUID and the merged snapshot is removed. For information on using this option, see 第 5.4.8 节 “Merging Snapshot Volumes”.

3.3.7. Thinly-Provisioned Snapshot Volumes
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The Red Hat Enterprise Linux release 6.4 version of LVM provides support for thinly-provisioned snapshot volumes. Thin snapshot volumes allow many virtual devices to be stored on the same data volume. This simplifies administration and allows for the sharing of data between snapshot volumes.
As for all LVM snapshot volumes, as well as all thin volumes, thin snapshot volumes are not supported across the nodes in a cluster. The snapshot volume must be exclusively activated on only one cluster node.
Thin snapshot volumes provide the following benefits:
  • A thin snapshot volume can reduce disk usage when there are multiple snapshots of the same origin volume.
  • If there are multiple snapshots of the same origin, then a write to the origin will cause one COW operation to preserve the data. Increasing the number of snapshots of the origin should yield no major slowdown.
  • Thin snapshot volumes can be used as a logical volume origin for another snapshot. This allows for an arbitrary depth of recursive snapshots (snapshots of snapshots of snapshots...).
  • A snapshot of a thin logical volume also creates a thin logical volume. This consumes no data space until a COW operation is required, or until the snapshot itself is written.
  • A thin snapshot volume does not need to be activated with its origin, so a user may have only the origin active while there are many inactive snapshot volumes of the origin.
  • When you delete the origin of a thinly-provisioned snapshot volume, each snapshot of that origin volume becomes an independent thinly-provisioned volume. This means that instead of merging a snapshot with its origin volume, you may choose to delete the origin volume and then create a new thinly-provisioned snapshot using that independent volume as the origin volume for the new snapshot.
Although there are many advantages to using thin snapshot volumes, there are some use cases for which the older LVM snapshot volume feature may be more appropriate to your needs:
  • You cannot change the chunk size of a thin pool. If the thin pool has a large chunk size (for example, 1MB) and you require a short-living snapshot for which a chunk size that large is not efficient, you may elect to use the older snapshot feature.
  • You cannot limit the size of a thin snapshot volume; the snapshot will use all of the space in the thin pool, if necessary. This may not be appropriate for your needs.
In general, you should consider the specific requirements of your site when deciding which snapshot format to use.
For information on configuring thin snapshot volumes, see 第 5.4.6 节 “Creating Thinly-Provisioned Snapshot Volumes”.

3.3.8. Cache Volumes
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As of the Red Hat Enterprise Linux 6.7 release, LVM supports the use of fast block devices (such as SSD drives) as write-back or write-though caches for larger slower block devices. Users can create cache logical volumes to improve the performance of their existing logical volumes or create new cache logical volumes composed of a small and fast device coupled with a large and slow device.
For information on creating LVM cache volumes, see 第 5.4.7 节 “Creating LVM Cache Logical Volumes”.

第 4 章 LVM 管理总览
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This chapter provides an overview of the administrative procedures you use to configure LVM logical volumes. This chapter is intended to provide a general understanding of the steps involved. For specific step-by-step examples of common LVM configuration procedures, see 第 6 章 LVM 配置示例.
For descriptions of the CLI commands you can use to perform LVM administration, see 第 5 章 用 CLI 命令管理 LVM. Alternately, you can use the LVM GUI, which is described in 第 8 章 用 LVM GUI 进行 LVM 管理.

4.1. 在群集中创建 LVM 卷
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To create logical volumes in a cluster environment, you use the Clustered Logical Volume Manager (CLVM), which is a set of clustering extensions to LVM. These extensions allow a cluster of computers to manage shared storage (for example, on a SAN) using LVM. In order to use CLVM, the High Availability Add-On and Resilient Storage Add-On software, including the clvmd daemon, must be started at boot time, as described in 第 2.4 节 “群集逻辑卷管理器（CLVM）”.
在群集环境中创建 LVM 逻辑卷和在单一节点创建 LVM 逻辑卷是一样的。LVM 命令本身没有什么不同，LVM GUI 界面也一样。要启用您在群集中创建的 LVM 卷，群集构架必须正在运行且群集必须有足够节点。
CLVM requires changes to the lvm.conf file for cluster-wide locking. Information on configuring the lvm.conf file to support clustered locking is provided within the lvm.conf file itself. For information about the lvm.conf file, see 附录 B, LVM 配置文件.
By default, logical volumes created with CLVM on shared storage are visible to all systems that have access to the shared storage. It is possible to create volume groups in which all of the storage devices are visible to only one node in the cluster. It is also possible to change the status of a volume group from a local volume group to a clustered volume group. For information, see 第 5.3.3 节 “在群集中创建卷组” and 第 5.3.8 节 “修改卷组参数”

警告

When you create volume groups with CLVM on shared storage, you must ensure that all nodes in the cluster have access to the physical volumes that constitute the volume group. Asymmetric cluster configurations in which some nodes have access to the storage and others do not are not supported.
For information on how to install the High Availability Add-On and set up the cluster infrastructure, see Cluster Administration.
For an example of creating a mirrored logical volume in a cluster, see 第 6.5 节 “Creating a Mirrored LVM Logical Volume in a Cluster”.

4.2. 创建逻辑卷总览
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以下内容对创建 LVM 逻辑卷的步骤进行了总结。
  1. 将您要用作 LVM 卷的分区初始化为物理卷（进行标记）。
  2. 创建卷组。
  3. 创建逻辑卷。
After creating the logical volume you can create and mount the file system. The examples in this document use GFS2 file systems.

注意

Although a GFS2 file system can be implemented in a standalone system or as part of a cluster configuration, for the Red Hat Enterprise Linux 6 release Red Hat does not support the use of GFS2 as a single-node file system. Red Hat will continue to support single-node GFS2 file systems for mounting snapshots of cluster file systems (for example, for backup purposes).
  1. Create a GFS2 file system on the logical volume with the mkfs.gfs2 command.
  2. 用 mkdir 命令创建一个新的挂载点。在群集的系统中，在群集的所有节点中创建挂载点。
  3. 挂载文件系统。您可能想要在 fstab 为系统中的每个节点添加一行。
Alternately, you can create and mount the GFS2 file system with the LVM GUI.
创建 LVM 卷在每台机器上都是不同的，因为保存 LVM 设置信息的区域是在物理卷中，而不是在创建卷的机器中。用于存储的服务器有本地副本，但可以重新生成物理卷中的内容。如果 LVM 版本兼容，您可以将物理卷附加到不同服务器上。

4.3. 在逻辑卷中增大文件系统
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要在逻辑卷中增大文件系统，请按以下步骤执行：
  1. 创建一个新的物理卷。
  2. 扩展带有您想要增大的文件系统逻辑卷的卷组，使其包含新的物理卷。
  3. 扩展逻辑卷使其包含新的物理卷。
  4. 增大文件系统。
如果您的卷组中有足够的未分配空间，您可以使用那些空间来扩展逻辑卷，而不执行步骤 1 和 2。

4.4. 逻辑卷备份
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Metadata backups and archives are automatically created on every volume group and logical volume configuration change unless disabled in the lvm.conf file. By default, the metadata backup is stored in the /etc/lvm/backup file and the metadata archives are stored in the /etc/lvm/archive file. How long the metadata archives stored in the /etc/lvm/archive file are kept and how many archive files are kept is determined by parameters you can set in the lvm.conf file. A daily system backup should include the contents of the /etc/lvm directory in the backup.
注意：元数据备份并不包含逻辑卷中的用户和系统数据。
You can manually back up the metadata to the /etc/lvm/backup file with the vgcfgbackup command. You can restore metadata with the vgcfgrestore command. The vgcfgbackup and vgcfgrestore commands are described in 第 5.3.13 节 “备份卷组元数据”.

4.5. 日志
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所有信息输出都是通过日志模块传递，日志模式根据日志级别有不同的选择：
  • 标准输出/错误
  • 系统日志
  • 日志文件
  • 外部日志功能
The logging levels are set in the /etc/lvm/lvm.conf file, which is described in 附录 B, LVM 配置文件.

4.6. The Metadata Daemon (lvmetad)
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LVM can optionally use a central metadata cache, implemented through a daemon (lvmetad) and a udev rule. The metadata daemon has two main purposes: It improves performance of LVM commands and it allows udev to automatically activate logical volumes or entire volume groups as they become available to the system.

注意

The lvmetad daemon is not currently supported across the nodes of a cluster, and requires that the locking type be local file-based locking.
To take advantage of the daemon, you must do the following:
  • Start the daemon through the lvm2-lvmetad service. To start the daemon automatically at boot time, use the chkconfig lvm2-lvmetad on command. To start the daemon manually, use the service lvm2-lvmetad start command.
  • Configure LVM to make use of the daemon by setting the global/use_lvmetad variable to 1 in the lvm.conf configuration file. For information on the lvm.conf configuration file, see 附录 B, LVM 配置文件.
Normally, each LVM command issues a disk scan to find all relevant physical volumes and to read volume group metadata. However, if the metadata daemon is running and enabled, this expensive scan can be skipped. Instead, the lvmetad daemon scans each device only once, when it becomes available, by means of udev rules. This can save a significant amount of I/O and reduce the time required to complete LVM operations, particularly on systems with many disks. For information on the udev device manager and udev rules, see 第 A.3 节 “Device Mapper Support for the udev Device Manager”.
When a new volume group is made available at runtime (for example, through hotplug or iSCSI), its logical volumes must be activated in order to be used. When the lvmetad daemon is enabled, the activation/auto_activation_volume_list option in the lvm.conf configuration file can be used to configure a list of volume groups and logical volumes that should be automatically activated. Without the lvmetad daemon, a manual activation is necessary. By default, this list is not defined, which means that all volumes are autoactivated once all of the physical volumes are in place. The autoactivation works recursively for LVM stacked on top of other devices, as it is event-based.

注意

When the lvmetad daemon is running, the filter = setting in the /etc/lvm/lvm.conf file does not apply when you execute the pvscan --cache device command. To filter devices, you need to use the global_filter = setting. Devices that fail the global filter are not opened by LVM and are never scanned. You may need to use a global filter, for example, when you use LVM devices in VMs and you do not want the contents of the devices in the VMs to be scanned by the physical host.

4.7. Displaying LVM Information with the lvm Command
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The lvm command provides several built-in options that you can use to display information about LVM support and configuration.
  • lvm devtypes
    Displays the recognized built-in block device types (Red Hat Enterprise Linux release 6.6 and later).
  • lvm formats
    Displays recognizes metadata formats.
  • lvm help
    Displays LVM help text.
  • lvm segtypes
    Displays recognized logical volume segment types.
  • lvm tags
    Displays any tags defined on this host. For information on LVM object tags, see 附录 D, LVM 对象标签.
  • lvm version
    Displays the current version information.

第 5 章 用 CLI 命令管理 LVM
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本章总结了您可使用 LVM 命令行界面（CLI）来创建和维护逻辑卷的独立管理任务。

注意

If you are creating or modifying an LVM volume for a clustered environment, you must ensure that you are running the clvmd daemon. For information, see 第 4.1 节 “在群集中创建 LVM 卷”.

5.1. 使用 CLI 命令
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LVM CLI 命令有一些通用的特性。
当在命令行中需要容量参数时，可以明确指定单位。如果您不指定单位，那么就使用默认的 KB 或者 MB。LVM CLI 不接受分数。
在命令行参数中为 LVM 指定单位时要无需区分大小写，比如 M 或者 m 的效果是一样的，且使用 2 的乘方（乘 1024）。但是，在某个命令中指定 --units 参数时，小写表示该单位乘 1024，而大写表示该单位乘 1000。
Where commands take volume group or logical volume names as arguments, the full path name is optional. A logical volume called lvol0 in a volume group called vg0 can be specified as vg0/lvol0. Where a list of volume groups is required but is left empty, a list of all volume groups will be substituted. Where a list of logical volumes is required but a volume group is given, a list of all the logical volumes in that volume group will be substituted. For example, the lvdisplay vg0 command will display all the logical volumes in volume group vg0.
所有 LVM 命令都接受 -v 参数，它可多次输入来提高输出的详细程度。例如：以下示例显示的是 lvcreate 命令的默认输出。 
# lvcreate -L 50MB new_vg
  Rounding up size to full physical extent 52.00 MB
  Logical volume "lvol0" created
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下面是 lvcreate 命令带 -v 参数的输出。 
# lvcreate -v -L 50MB new_vg
    Finding volume group "new_vg"
  Rounding up size to full physical extent 52.00 MB
    Archiving volume group "new_vg" metadata (seqno 4).
    Creating logical volume lvol0
    Creating volume group backup "/etc/lvm/backup/new_vg" (seqno 5).
    Found volume group "new_vg"
    Creating new_vg-lvol0
    Loading new_vg-lvol0 table
    Resuming new_vg-lvol0 (253:2)
    Clearing start of logical volume "lvol0"
    Creating volume group backup "/etc/lvm/backup/new_vg" (seqno 5).
  Logical volume "lvol0" created
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您还可以使用 -vv、-vvv 或者 -vvvv 参数来提高命令执行的详细程度。-vvvv 参数可以提供最多的信息。以下是 lvcreate 命令带 -vvvv 参数时给出的输出的前几行。 
# lvcreate -vvvv -L 50MB new_vg
#lvmcmdline.c:913         Processing: lvcreate -vvvv -L 50MB new_vg
#lvmcmdline.c:916         O_DIRECT will be used
#config/config.c:864       Setting global/locking_type to 1
#locking/locking.c:138       File-based locking selected.
#config/config.c:841       Setting global/locking_dir to /var/lock/lvm
#activate/activate.c:358       Getting target version for linear
#ioctl/libdm-iface.c:1569         dm version   OF   [16384]
#ioctl/libdm-iface.c:1569         dm versions   OF   [16384]
#activate/activate.c:358       Getting target version for striped
#ioctl/libdm-iface.c:1569         dm versions   OF   [16384]
#config/config.c:864       Setting activation/mirror_region_size to 512
...
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您可以用命令的 --help 参数来显示任意 LVM CLI 命令的帮助信息。 
# commandname --help
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要显示某个命令的 man page，请执行 man 命令： 
# man commandname
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man lvm 命令提供有关 LVM 的常规在线信息。
All LVM objects are referenced internally by a UUID, which is assigned when you create the object. This can be useful in a situation where you remove a physical volume called /dev/sdf which is part of a volume group and, when you plug it back in, you find that it is now /dev/sdk. LVM will still find the physical volume because it identifies the physical volume by its UUID and not its device name. For information on specifying the UUID of a physical volume when creating a physical volume, see 第 7.4 节 “修复物理卷元数据”.

5.2. 物理卷管理
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这部分论述了对物理卷不同方面进行管理的命令。

5.2.1. 创建物理卷
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下面的子部分论述了创建物理卷的命令。
5.2.1.1. 设定分区类型
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如果您将整张磁盘作为您的物理卷使用，那么磁盘就必须没有分区表。对于 DOS 磁盘分区，您应该用 fdisk 或者 cfdisk 或者等同的命令将分区 id 设为 0x8e。如果将整张磁盘作为一个设备使用就必须擦除分区表，这也就会有效地破坏磁盘中的数据。您可以用以下命令将现有分区表的第一个扇区归零，从而删除分区表： 
# dd if=/dev/zero of=PhysicalVolume bs=512 count=1
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5.2.1.2. 初始化物理卷
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使用 pvcreate 命令来将一个块设备初始化为一个物理卷。初始化和格式化文件系统类似。
The following command initializes /dev/sdd, /dev/sde, and /dev/sdf as LVM physical volumes for later use as part of LVM logical volumes. 
# pvcreate /dev/sdd /dev/sde /dev/sdf
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To initialize partitions rather than whole disks: run the pvcreate command on the partition. The following example initializes the partition /dev/hdb1 as an LVM physical volume for later use as part of an LVM logical volume. 
# pvcreate /dev/hdb1
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5.2.1.3. 扫描块设备
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您可以使用 lvmdiskscan 命令来扫描用作物理卷的块设备，示例如下。 
# lvmdiskscan
  /dev/ram0                    [       16.00 MB]
  /dev/sda                     [       17.15 GB]
  /dev/root                    [       13.69 GB]
  /dev/ram                     [       16.00 MB]
  /dev/sda1                    [       17.14 GB] LVM physical volume
  /dev/VolGroup00/LogVol01     [      512.00 MB]
  /dev/ram2                    [       16.00 MB]
  /dev/new_vg/lvol0            [       52.00 MB]
  /dev/ram3                    [       16.00 MB]
  /dev/pkl_new_vg/sparkie_lv   [        7.14 GB]
  /dev/ram4                    [       16.00 MB]
  /dev/ram5                    [       16.00 MB]
  /dev/ram6                    [       16.00 MB]
  /dev/ram7                    [       16.00 MB]
  /dev/ram8                    [       16.00 MB]
  /dev/ram9                    [       16.00 MB]
  /dev/ram10                   [       16.00 MB]
  /dev/ram11                   [       16.00 MB]
  /dev/ram12                   [       16.00 MB]
  /dev/ram13                   [       16.00 MB]
  /dev/ram14                   [       16.00 MB]
  /dev/ram15                   [       16.00 MB]
  /dev/sdb                     [       17.15 GB]
  /dev/sdb1                    [       17.14 GB] LVM physical volume
  /dev/sdc                     [       17.15 GB]
  /dev/sdc1                    [       17.14 GB] LVM physical volume
  /dev/sdd                     [       17.15 GB]
  /dev/sdd1                    [       17.14 GB] LVM physical volume
  7 disks
  17 partitions
  0 LVM physical volume whole disks
  4 LVM physical volumes
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5.2.2. 显示物理卷
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用来显示 LVM 物理卷属性的命令有三个：pvs、pvdisplay 和 pvscan。
The pvs command provides physical volume information in a configurable form, displaying one line per physical volume. The pvs command provides a great deal of format control, and is useful for scripting. For information on using the pvs command to customize your output, see 第 5.8 节 “为 LVM 自定义报告”.
The pvdisplay command provides a verbose multi-line output for each physical volume. It displays physical properties (size, extents, volume group, and so on) in a fixed format.
以下是 pvdisplay 为单一物理卷显示的输出结果示例。 
# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               new_vg
  PV Size               17.14 GB / not usable 3.40 MB
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              4388
  Free PE               4375
  Allocated PE          13
  PV UUID               Joqlch-yWSj-kuEn-IdwM-01S9-XO8M-mcpsVe
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pvscan 命令在系统中为物理卷扫描所有支持的 LVM 块设备。
以下命令显示所有找到的物理设备： 
# pvscan
 PV /dev/sdb2   VG vg0   lvm2 [964.00 MB / 0   free]
 PV /dev/sdc1   VG vg0   lvm2 [964.00 MB / 428.00 MB free]
 PV /dev/sdc2            lvm2 [964.84 MB]
 Total: 3 [2.83 GB] / in use: 2 [1.88 GB] / in no VG: 1 [964.84 MB]
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You can define a filter in the /etc/lvm/lvm.conf file so that this command will avoid scanning specific physical volumes. For information on using filters to control which devices are scanned, see 第 5.5 节 “用过滤器控制 LVM 设备扫描”.

5.2.3. 防止在物理卷中进行分配
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您可以使用 pvchange 命令防止在一个或者多个物理卷的剩余空间进行物理扩展分配。这在出现磁盘错误或者要删除物理卷时是很必要的。
The following command disallows the allocation of physical extents on /dev/sdk1. 
# pvchange -x n /dev/sdk1
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您还可以使用 pvchange 命令的 -xy 参数来允许在之前禁止进行分配的地方分配扩展。

5.2.4. 重新设置物理卷大小
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如果您由于任何原因需要修改基本块设备的大小，请使用 pvresize 命令来更新 LVM 的大小。您可以在 LVM 正在使用物理卷的时候使用这个命令。

5.2.5. 删除物理卷
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如果 LVM 不再使用某个设备，您可以使用 pvremove 命令删除 LVM 标签。执行 pvremove 会将空白物理卷的 LVM 元数据归零。
If the physical volume you want to remove is currently part of a volume group, you must remove it from the volume group with the vgreduce command, as described in 第 5.3.7 节 “从卷组中删除物理卷”. 
# pvremove /dev/ram15
  Labels on physical volume "/dev/ram15" successfully wiped
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5.3. 卷组管理
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这部分论述用于管理卷组各个方面的命令。

5.3.1. 创建卷组
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To create a volume group from one or more physical volumes, use the vgcreate command. The vgcreate command creates a new volume group by name and adds at least one physical volume to it.
The following command creates a volume group named vg1 that contains physical volumes /dev/sdd1 and /dev/sde1. 
# vgcreate vg1 /dev/sdd1 /dev/sde1
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当使用物理卷创建卷组时，默认情况下，它的磁盘空间被分成大小为 4MB 的扩展。这个扩展是增大或者减小逻辑卷容量的最小单位。大量的扩展不会影响逻辑卷的 I/O 性能。
You can specify the extent size with the -s option to the vgcreate command if the default extent size is not suitable. You can put limits on the number of physical or logical volumes the volume group can have by using the -p and -l arguments of the vgcreate command.
By default, a volume group allocates physical extents according to common-sense rules such as not placing parallel stripes on the same physical volume. This is the normal allocation policy. You can use the --alloc argument of the vgcreate command to specify an allocation policy of contiguous, anywhere, or cling. In general, allocation policies other than normal are required only in special cases where you need to specify unusual or nonstandard extent allocation. For further information on how LVM allocates physical extents, see 第 5.3.2 节 “LVM Allocation”.
LVM 卷组和基本逻辑卷是包含在 /dev 目录的设备专用文件目录树中的，布局如下： 
/dev/vg/lv/
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For example, if you create two volume groups myvg1 and myvg2, each with three logical volumes named lv01, lv02, and lv03, six device special files are created: 
/dev/myvg1/lv01
/dev/myvg1/lv02
/dev/myvg1/lv03
/dev/myvg2/lv01
/dev/myvg2/lv02
/dev/myvg2/lv03
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The device special files are not present if the corresponding logical volume is not currently active.
64 位 CPU 中 LVM 的最大设备大小为 8EB。

5.3.2. LVM Allocation
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When an LVM operation needs to allocate physical extents for one or more logical volumes, the allocation proceeds as follows:
  • The complete set of unallocated physical extents in the volume group is generated for consideration. If you supply any ranges of physical extents at the end of the command line, only unallocated physical extents within those ranges on the specified physical volumes are considered.
  • Each allocation policy is tried in turn, starting with the strictest policy (contiguous) and ending with the allocation policy specified using the --alloc option or set as the default for the particular logical volume or volume group. For each policy, working from the lowest-numbered logical extent of the empty logical volume space that needs to be filled, as much space as possible is allocated, according to the restrictions imposed by the allocation policy. If more space is needed, LVM moves on to the next policy.
The allocation policy restrictions are as follows:
  • An allocation policy of contiguous requires that the physical location of any logical extent that is not the first logical extent of a logical volume is adjacent to the physical location of the logical extent immediately preceding it.
    When a logical volume is striped or mirrored, the contiguous allocation restriction is applied independently to each stripe or mirror image (leg) that needs space.
  • An allocation policy of cling requires that the physical volume used for any logical extent to be added to an existing logical volume is already in use by at least one logical extent earlier in that logical volume. If the configuration parameter allocation/cling_tag_list is defined, then two physical volumes are considered to match if any of the listed tags is present on both physical volumes. This allows groups of physical volumes with similar properties (such as their physical location) to be tagged and treated as equivalent for allocation purposes. For more information on using the cling policy in conjunction with LVM tags to specify which additional physical volumes to use when extending an LVM volume, see 第 5.4.14.3 节 “Extending a Logical Volume with the cling Allocation Policy”.
    When a Logical Volume is striped or mirrored, the cling allocation restriction is applied independently to each stripe or mirror image (leg) that needs space.
  • An allocation policy of normal will not choose a physical extent that shares the same physical volume as a logical extent already allocated to a parallel logical volume (that is, a different stripe or mirror image/leg) at the same offset within that parallel logical volume.
    When allocating a mirror log at the same time as logical volumes to hold the mirror data, an allocation policy of normal will first try to select different physical volumes for the log and the data. If that is not possible and the allocation/mirror_logs_require_separate_pvs configuration parameter is set to 0, it will then allow the log to share physical volume(s) with part of the data.
    Similarly, when allocating thin pool metadata, an allocation policy of normal will follow the same considerations as for allocation of a mirror log, based on the value of the allocation/thin_pool_metadata_require_separate_pvs configuration parameter.
  • If there are sufficient free extents to satisfy an allocation request but a normal allocation policy would not use them, the anywhere allocation policy will, even if that reduces performance by placing two stripes on the same physical volume.
The allocation policies can be changed using the vgchange command.

注意

If you rely upon any layout behavior beyond that documented in this section according to the defined allocation policies, you should note that this might change in future versions of the code. For example, if you supply on the command line two empty physical volumes that have an identical number of free physical extents available for allocation, LVM currently considers using each of them in the order they are listed; there is no guarantee that future releases will maintain that property. If it is important to obtain a specific layout for a particular Logical Volume, then you should build it up through a sequence of lvcreate and lvconvert steps such that the allocation policies applied to each step leave LVM no discretion over the layout.
To view the way the allocation process currently works in any specific case, you can read the debug logging output, for example by adding the -vvvv option to a command.

5.3.3. 在群集中创建卷组
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在群集环境中使用 vgcreate 命令创建卷组就如同在单一节点中创建卷组。
By default, volume groups created with CLVM on shared storage are visible to all computers that have access to the shared storage. It is possible, however, to create volume groups that are local, visible only to one node in the cluster, by using the -c n option of the vgcreate command.
The following command, when executed in a cluster environment, creates a volume group that is local to the node from which the command was executed. The command creates a local volume named vg1 that contains physical volumes /dev/sdd1 and /dev/sde1. 
# vgcreate -c n vg1 /dev/sdd1 /dev/sde1
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You can change whether an existing volume group is local or clustered with the -c option of the vgchange command, which is described in 第 5.3.8 节 “修改卷组参数”.
You can check whether an existing volume group is a clustered volume group with the vgs command, which displays the c attribute if the volume is clustered. The following command displays the attributes of the volume groups VolGroup00 and testvg1. In this example, VolGroup00 is not clustered, while testvg1 is clustered, as indicated by the c attribute under the Attr heading. 
# vgs
  VG            #PV #LV #SN Attr   VSize  VFree
  VolGroup00      1   2   0 wz--n- 19.88G    0
  testvg1         1   1   0 wz--nc 46.00G 8.00M
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For more information on the vgs command, see 第 5.3.5 节 “显示卷组”第 5.8 节 “为 LVM 自定义报告”, and the vgs man page.

5.3.4. 在卷组中添加物理卷
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To add additional physical volumes to an existing volume group, use the vgextend command. The vgextend command increases a volume group's capacity by adding one or more free physical volumes.
The following command adds the physical volume /dev/sdf1 to the volume group vg1. 
# vgextend vg1 /dev/sdf1
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5.3.5. 显示卷组
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您可以使用两个命令来显示 LVM 卷组的属性：vgs 和 vgdisplay。
The vgscan command, which scans all the disks for volume groups and rebuilds the LVM cache file, also displays the volume groups. For information on the vgscan command, see 第 5.3.6 节 “为卷组扫描磁盘来建立缓存文件”.
The vgs command provides volume group information in a configurable form, displaying one line per volume group. The vgs command provides a great deal of format control, and is useful for scripting. For information on using the vgs command to customize your output, see 第 5.8 节 “为 LVM 自定义报告”.
The vgdisplay command displays volume group properties (such as size, extents, number of physical volumes, and so on) in a fixed form. The following example shows the output of a vgdisplay command for the volume group new_vg. If you do not specify a volume group, all existing volume groups are displayed. 
# vgdisplay new_vg
  --- Volume group ---
  VG Name               new_vg
  System ID
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  11
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               51.42 GB
  PE Size               4.00 MB
  Total PE              13164
  Alloc PE / Size       13 / 52.00 MB
  Free  PE / Size       13151 / 51.37 GB
  VG UUID               jxQJ0a-ZKk0-OpMO-0118-nlwO-wwqd-fD5D32
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5.3.6. 为卷组扫描磁盘来建立缓存文件
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The vgscan command scans all supported disk devices in the system looking for LVM physical volumes and volume groups. This builds the LVM cache file in the /etc/lvm/cache/.cache file, which maintains a listing of current LVM devices.
LVM runs the vgscan command automatically at system startup and at other times during LVM operation, such as when you execute a vgcreate command or when LVM detects an inconsistency.

注意

You may need to run the vgscan command manually when you change your hardware configuration and add or delete a device from a node, causing new devices to be visible to the system that were not present at system bootup. This may be necessary, for example, when you add new disks to the system on a SAN or hotplug a new disk that has been labeled as a physical volume.
You can define a filter in the lvm.conf file to restrict the scan to avoid specific devices. For information on using filters to control which devices are scanned, see 第 5.5 节 “用过滤器控制 LVM 设备扫描”.
下面的例子显示了 vgscan 命令的输出结果。 
# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "new_vg" using metadata type lvm2
  Found volume group "officevg" using metadata type lvm2
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5.3.7. 从卷组中删除物理卷
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To remove unused physical volumes from a volume group, use the vgreduce command. The vgreduce command shrinks a volume group's capacity by removing one or more empty physical volumes. This frees those physical volumes to be used in different volume groups or to be removed from the system.
在您从卷组中删除物理卷之前，您可以使用 pvdisplay 命令确定物理卷没有被任何逻辑卷使用。 
# pvdisplay /dev/hda1

-- Physical volume ---
PV Name               /dev/hda1
VG Name               myvg
PV Size               1.95 GB / NOT usable 4 MB [LVM: 122 KB]
PV#                   1
PV Status             available
Allocatable           yes (but full)
Cur LV                1
PE Size (KByte)       4096
Total PE              499
Free PE               0
Allocated PE          499
PV UUID               Sd44tK-9IRw-SrMC-MOkn-76iP-iftz-OVSen7
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If the physical volume is still being used you will have to migrate the data to another physical volume using the pvmove command. Then use the vgreduce command to remove the physical volume.
The following command removes the physical volume /dev/hda1 from the volume group my_volume_group. 
# vgreduce my_volume_group /dev/hda1
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If a logical volume contains a physical volume that fails, you cannot use that logical volume. To remove missing physical volumes from a volume group, you can use the --removemissing parameter of the vgreduce command, if there are no logical volumes that are allocated on the missing physical volumes.

5.3.8. 修改卷组参数
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The vgchange command is used to deactivate and activate volume groups, as described in 第 5.3.9 节 “激活和失活卷组”. You can also use this command to change several volume group parameters for an existing volume group.
The following command changes the maximum number of logical volumes of volume group vg00 to 128. 
# vgchange -l 128 /dev/vg00
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有关 vgchange 命令的卷组参数的论述请参考 vgchange(8) man page。

5.3.9. 激活和失活卷组
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当您创建一个卷组时，默认情况下它是激活的。这就是说该组中的逻辑卷是可访问，也可修改的。
There are various circumstances for which you need to make a volume group inactive and thus unknown to the kernel. To deactivate or activate a volume group, use the -a (--available) argument of the vgchange command.
The following example deactivates the volume group my_volume_group. 
# vgchange -a n my_volume_group
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如果启用了群集的锁定，添加‘e’来激活或者失活完全占据一个节点的卷组，或者添加‘l’来激活或者失活只位于本地节点的卷组。带单一主机快照的逻辑卷总是被完全激活，因为他们一次只能在一个节点上使用。
You can deactivate individual logical volumes with the lvchange command, as described in 第 5.4.10 节 “修改逻辑卷组的参数”, For information on activating logical volumes on individual nodes in a cluster, see 第 5.7 节 “在群集的独立节点中激活逻辑卷”.

5.3.10. 删除卷组
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要删除不包含逻辑卷的卷组，请使用 vgremove 命令。 
# vgremove officevg
  Volume group "officevg" successfully removed
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5.3.11. 分割卷组
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要分割卷组的物理卷并创建新的卷组，请使用 vgsplit 命令。
无法在卷组间分割逻辑卷。每个现有的逻辑卷必须完整地存在于物理卷中来构成旧的或者新的卷组。如果需要，您可以使用 pvmove 命令来进行强制分割。
The following example splits off the new volume group smallvg from the original volume group bigvg. 
# vgsplit bigvg smallvg /dev/ram15
  Volume group "smallvg" successfully split from "bigvg"
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5.3.12. 合并卷组
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To combine two volume groups into a single volume group, use the vgmerge command. You can merge an inactive "source" volume with an active or an inactive "destination" volume if the physical extent sizes of the volume are equal and the physical and logical volume summaries of both volume groups fit into the destination volume groups limits.
The following command merges the inactive volume group my_vg into the active or inactive volume group databases giving verbose runtime information. 
# vgmerge -v databases my_vg
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5.3.13. 备份卷组元数据
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在每次修改卷组和逻辑卷配置时都会自动进行元数据备份和归档，除非您在 lvm.conf 文件中禁用该功能。在默认情况下，元数据备份保存在 /etc/lvm/backup 文件中，元数据归档保存在 /etc/lvm/archives 中。您可以手动使用 vgcfgbackup 命令将元数据备份到 /etc/lvm/backup 文件中。
vgcfrestore 命令可为卷组中的所有物理卷从归档中恢复卷组的元数据。
For an example of using the vgcfgrestore command to recover physical volume metadata, see 第 7.4 节 “修复物理卷元数据”.

5.3.14. 重命名卷组
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使用 vgrename 命令来重新命名一个现有的卷组。
Either of the following commands renames the existing volume group vg02 to my_volume_group 
# vgrename /dev/vg02 /dev/my_volume_group
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# vgrename vg02 my_volume_group
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5.3.15. 将卷组移动到其它系统中
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您可以将整个 LVM 卷组移动到另一个系统中。建议您使用 vgexport 和 vgimport 命令进行此操作。

注意

As of Red Hat Enterprise Linux 6.5, you can use the --force argument of the vgimport command. This allows you to import volume groups that are missing physical volumes and subsequently run the vgreduce --removemissing command.
vgexport 使系统无法访问失活卷组，这样可允许您卸去其物理卷。vgimport 命令可在 vgexport 命令使卷组失活后让机器可以重新访问该卷组。
要将一个卷组从一个系统移动到另一个系统，请执行以下步骤：
  1. 确定没有用户正在访问卷组中激活卷中的文件，然后卸载逻辑卷。
  2. 使用 vgchange 命令的 -a n 参数将卷组标记为失活，这样可防止在该卷组中进行任何进一步的操作。
  3. 使用 vgexport 命令导出卷组。这样可防止您要将其从中删除的系统访问该卷组。
    在您导出卷组后，在执行 pvscan 命令时，物理卷会在导出的物理卷中显示，如下。 
    # pvscan
  PV /dev/sda1    is in exported VG myvg [17.15 GB / 7.15 GB free]
  PV /dev/sdc1    is in exported VG myvg [17.15 GB / 15.15 GB free]
  PV /dev/sdd1   is in exported VG myvg [17.15 GB / 15.15 GB free]
  ...
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    当关闭系统时，您可以拔出组成该卷组的磁盘并将它们连接到新的系统中。
  4. 当将磁盘插入新的系统，使用 vgimport 命令导入卷组，并使新的系统可以访问该卷组。
  5. 用 vgchange 命令的 -a y 参数激活卷组。
  6. 挂载文件系统使其可用。

5.3.16. 重新创建卷组目录
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To recreate a volume group directory and logical volume special files, use the vgmknodes command. This command checks the LVM2 special files in the /dev directory that are needed for active logical volumes. It creates any special files that are missing removes unused ones.
You can incorporate the vgmknodes command into the vgscan command by specifying the mknodes argument to the vgscan command.

5.4. 逻辑卷管理
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这部分介绍了逻辑卷管理各个方面的命令。

5.4.1. Creating Linear Logical Volumes
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To create a logical volume, use the lvcreate command. If you do not specify a name for the logical volume, the default name lvol# is used where # is the internal number of the logical volume.
当您创建逻辑卷时，该逻辑卷是从使用物理卷可用扩展的卷组中切割下来的，它们构成了卷组。通常逻辑卷会根据下一个可用原则在最大程度上使用基本物理卷中的空间。修改逻辑卷可释放并重新分配物理卷的空间。
As of the Red Hat Enterprise Linux 6.3 release, you can use LVM to create, display, rename, use, and remove RAID logical volumes. For information on RAID logical volumes, see 第 5.4.16 节 “RAID Logical Volumes”.
The following command creates a logical volume 10 gigabytes in size in the volume group vg1. 
# lvcreate -L 10G vg1
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The default unit for logical volume size is megabytes. The following command creates a 1500 MB linear logical volume named testlv in the volume group testvg, creating the block device /dev/testvg/testlv. 
# lvcreate -L 1500 -n testlv testvg
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The following command creates a 50 gigabyte logical volume named gfslv from the free extents in volume group vg0. 
# lvcreate -L 50G -n gfslv vg0
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You can use the -l argument of the lvcreate command to specify the size of the logical volume in extents. You can also use this argument to specify the percentage of the volume group to use for the logical volume. The following command creates a logical volume called mylv that uses 60% of the total space in volume group testvg. 
# lvcreate -l 60%VG -n mylv testvg
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You can also use the -l argument of the lvcreate command to specify the percentage of the remaining free space in a volume group as the size of the logical volume. The following command creates a logical volume called yourlv that uses all of the unallocated space in the volume group testvg. 
# lvcreate -l 100%FREE -n yourlv testvg
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You can use -l argument of the lvcreate command to create a logical volume that uses the entire volume group. Another way to create a logical volume that uses the entire volume group is to use the vgdisplay command to find the "Total PE" size and to use those results as input to the lvcreate command.
The following commands create a logical volume called mylv that fills the volume group named testvg. 
# vgdisplay testvg | grep "Total PE"
Total PE              10230
# lvcreate -l 10230 testvg -n mylv
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The underlying physical volumes used to create a logical volume can be important if the physical volume needs to be removed, so you may need to consider this possibility when you create the logical volume. For information on removing a physical volume from a volume group, see 第 5.3.7 节 “从卷组中删除物理卷”.
To create a logical volume to be allocated from a specific physical volume in the volume group, specify the physical volume or volumes at the end at the lvcreate command line. The following command creates a logical volume named testlv in volume group testvg allocated from the physical volume /dev/sdg1, 
# lvcreate -L 1500 -ntestlv testvg /dev/sdg1
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You can specify which extents of a physical volume are to be used for a logical volume. The following example creates a linear logical volume out of extents 0 through 24 of physical volume /dev/sda1 and extents 50 through 124 of physical volume /dev/sdb1 in volume group testvg. 
# lvcreate -l 100 -n testlv testvg /dev/sda1:0-24 /dev/sdb1:50-124
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The following example creates a linear logical volume out of extents 0 through 25 of physical volume /dev/sda1 and then continues laying out the logical volume at extent 100. 
# lvcreate -l 100 -n testlv testvg /dev/sda1:0-25:100-
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The default policy for how the extents of a logical volume are allocated is inherit, which applies the same policy as for the volume group. These policies can be changed using the lvchange command. For information on allocation policies, see 第 5.3.1 节 “创建卷组”.

5.4.2. 创建条状卷
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For large sequential reads and writes, creating a striped logical volume can improve the efficiency of the data I/O. For general information about striped volumes, see 第 3.3.2 节 “条状逻辑卷”.
当您创建条状逻辑卷时，请使用 lvcreate 命令的 -i 参数指定条带的数目。这取决于逻辑卷要进行条带化的物理卷数目。条带的数目不能超过卷组中物理卷的数目（除非使用 --alloc anywhere 参数）。
如果构成逻辑卷的基本物理设备的大小不同，条状卷的最大容量由最小的基本设备决定。例如，在有两个分支条状卷中，其容量最大为较小设备的两倍。在有三个分支的条状卷中，其容量是最小设备的三倍。
The following command creates a striped logical volume across 2 physical volumes with a stripe of 64kB. The logical volume is 50 gigabytes in size, is named gfslv, and is carved out of volume group vg0. 
# lvcreate -L 50G -i2 -I64 -n gfslv vg0
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As with linear volumes, you can specify the extents of the physical volume that you are using for the stripe. The following command creates a striped volume 100 extents in size that stripes across two physical volumes, is named stripelv and is in volume group testvg. The stripe will use sectors 0-49 of /dev/sda1 and sectors 50-99 of /dev/sdb1. 
# lvcreate -l 100 -i2 -nstripelv testvg /dev/sda1:0-49 /dev/sdb1:50-99
  Using default stripesize 64.00 KB
  Logical volume "stripelv" created
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5.4.3. 创建镜像卷
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注意

As of the Red Hat Enterprise Linux 6.3 release, LVM supports RAID4/5/6 and a new implementation of mirroring. For information on this new implementation, see 第 5.4.16 节 “RAID Logical Volumes”.

注意

Creating a mirrored LVM logical volume in a cluster requires the same commands and procedures as creating a mirrored LVM logical volume on a single node. However, in order to create a mirrored LVM volume in a cluster the cluster and cluster mirror infrastructure must be running, the cluster must be quorate, and the locking type in the lvm.conf file must be set correctly to enable cluster locking. For an example of creating a mirrored volume in a cluster, see 第 6.5 节 “Creating a Mirrored LVM Logical Volume in a Cluster”.
Attempting to run multiple LVM mirror creation and conversion commands in quick succession from multiple nodes in a cluster might cause a backlog of these commands. This might cause some of the requested operations to time-out and, subsequently, fail. To avoid this issue, it is recommended that cluster mirror creation commands be executed from one node of the cluster.
当您创建一个镜像卷时，您可使用 lvcreate 命令的 -m 参数来指定数据的备份数目。指定 -m1 生成一个镜像，也就是生成两个文件系统副本：一个线性逻辑卷加上一个副本。同样的，指定 -m2 会生成两个镜像，也就是生成三个文件系统副本。
The following command creates a mirrored logical volume with a single mirror. The volume is 50 gigabytes in size, is named mirrorlv, and is carved out of volume group vg0: 
# lvcreate -L 50G -m1 -n mirrorlv vg0
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An LVM mirror divides the device being copied into regions that, by default, are 512KB in size. You can use the -R argument of the lvcreate command to specify the region size in megabytes. You can also change the default region size by editing the mirror_region_size setting in the lvm.conf file.

注意

Due to limitations in the cluster infrastructure, cluster mirrors greater than 1.5TB cannot be created with the default region size of 512KB. Users that require larger mirrors should increase the region size from its default to something larger. Failure to increase the region size will cause LVM creation to hang and may hang other LVM commands as well.
As a general guideline for specifying the region size for mirrors that are larger than 1.5TB, you could take your mirror size in terabytes and round up that number to the next power of 2, using that number as the -R argument to the lvcreate command. For example, if your mirror size is 1.5TB, you could specify -R 2. If your mirror size is 3TB, you could specify -R 4. For a mirror size of 5TB, you could specify -R 8.
The following command creates a mirrored logical volume with a region size of 2MB: 
# lvcreate -m1 -L 2T -R 2 -n mirror vol_group
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When a mirror is created, the mirror regions are synchronized. For large mirror components, the sync process may take a long time. As of the Red Hat Enterprise Linux 6.3 release, When you are creating a new mirror that does not need to be revived, you can specify the --nosync argument to indicate that an initial synchronization from the first device is not required.
LVM maintains a small log which it uses to keep track of which regions are in sync with the mirror or mirrors. By default, this log is kept on disk, which keeps it persistent across reboots and ensures that the mirror does not need to be resynced every time a machine reboots or crashes. You can specify instead that this log be kept in memory with the --mirrorlog core argument; this eliminates the need for an extra log device, but it requires that the entire mirror be resynchronized at every reboot.
The following command creates a mirrored logical volume from the volume group bigvg. The logical volume is named ondiskmirvol and has a single mirror. The volume is 12MB in size and keeps the mirror log in memory. 
# lvcreate -L 12MB -m1 --mirrorlog core -n ondiskmirvol bigvg
  Logical volume "ondiskmirvol" created
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镜像日志是在与生成镜像分支的设备不同的设备中生成的。但有可能使用 vgcreate 命令的 --alloc anywhere 参数在镜像分支之一的同一设备中创建镜像分支。这可能会降低性能，但可让您在只有两个基础设备的情况下创建镜像。
The following command creates a mirrored logical volume with a single mirror for which the mirror log is on the same device as one of the mirror legs. In this example, the volume group vg0 consists of only two devices. This command creates a 500 MB volume named mirrorlv in the vg0 volume group. 
# lvcreate -L 500M -m1 -n mirrorlv -alloc anywhere vg0
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注意

With clustered mirrors, the mirror log management is completely the responsibility of the cluster node with the currently lowest cluster ID. Therefore, when the device holding the cluster mirror log becomes unavailable on a subset of the cluster, the clustered mirror can continue operating without any impact, as long as the cluster node with lowest ID retains access to the mirror log. Since the mirror is undisturbed, no automatic corrective action (repair) is issued, either. When the lowest-ID cluster node loses access to the mirror log, however, automatic action will kick in (regardless of accessibility of the log from other nodes).
To create a mirror log that is itself mirrored, you can specify the --mirrorlog mirrored argument. The following command creates a mirrored logical volume from the volume group bigvg. The logical volume is named twologvol and has a single mirror. The volume is 12MB in size and the mirror log is mirrored, with each log kept on a separate device. 
# lvcreate -L 12MB -m1 --mirrorlog mirrored -n twologvol bigvg
  Logical volume "twologvol" created
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Just as with a standard mirror log, it is possible to create the redundant mirror logs on the same device as the mirror legs by using the --alloc anywhere argument of the vgcreate command. This may degrade performance, but it allows you to create a redundant mirror log even if you do not have sufficient underlying devices for each log to be kept on a separate device than the mirror legs.
When a mirror is created, the mirror regions are synchronized. For large mirror components, the sync process may take a long time. When you are creating a new mirror that does not need to be revived, you can specify the --nosync argument to indicate that an initial synchronization from the first device is not required.
You can specify which devices to use for the mirror legs and log, and which extents of the devices to use. To force the log onto a particular disk, specify exactly one extent on the disk on which it will be placed. LVM does not necessary respect the order in which devices are listed in the command line. If any physical volumes are listed that is the only space on which allocation will take place. Any physical extents included in the list that are already allocated will get ignored.
The following command creates a mirrored logical volume with a single mirror and a single log that is not mirrored. The volume is 500 MB in size, it is named mirrorlv, and it is carved out of volume group vg0. The first leg of the mirror is on device /dev/sda1, the second leg of the mirror is on device /dev/sdb1, and the mirror log is on /dev/sdc1. 
# lvcreate -L 500M -m1 -n mirrorlv vg0 /dev/sda1 /dev/sdb1 /dev/sdc1
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The following command creates a mirrored logical volume with a single mirror. The volume is 500 MB in size, it is named mirrorlv, and it is carved out of volume group vg0. The first leg of the mirror is on extents 0 through 499 of device /dev/sda1, the second leg of the mirror is on extents 0 through 499 of device /dev/sdb1, and the mirror log starts on extent 0 of device /dev/sdc1. These are 1MB extents. If any of the specified extents have already been allocated, they will be ignored. 
# lvcreate -L 500M -m1 -n mirrorlv vg0 /dev/sda1:0-499 /dev/sdb1:0-499 /dev/sdc1:0
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注意

As of the Red Hat Enterprise Linux 6.1 release, you can combine striping and mirroring in a single logical volume. Creating a logical volume while simultaneously specifying the number of mirrors (--mirrors X) and the number of stripes (--stripes Y) results in a mirror device whose constituent devices are striped.
5.4.3.1. Mirrored Logical Volume Failure Policy
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You can define how a mirrored logical volume behaves in the event of a device failure with the mirror_image_fault_policy and mirror_log_fault_policy parameters in the activation section of the lvm.conf file. When these parameters are set to remove, the system attempts to remove the faulty device and run without it. When this parameter is set to allocate, the system attempts to remove the faulty device and tries to allocate space on a new device to be a replacement for the failed device; this policy acts like the remove policy if no suitable device and space can be allocated for the replacement.
By default, the mirror_log_fault_policy parameter is set to allocate. Using this policy for the log is fast and maintains the ability to remember the sync state through crashes and reboots. If you set this policy to remove, when a log device fails the mirror converts to using an in-memory log and the mirror will not remember its sync status across crashes and reboots and the entire mirror will be resynced.
By default, the mirror_image_fault_policy parameter is set to remove. With this policy, if a mirror image fails the mirror will convert to a non-mirrored device if there is only one remaining good copy. Setting this policy to allocate for a mirror device requires the mirror to resynchronize the devices; this is a slow process, but it preserves the mirror characteristic of the device.

注意

When an LVM mirror suffers a device failure, a two-stage recovery takes place. The first stage involves removing the failed devices. This can result in the mirror being reduced to a linear device. The second stage, if the mirror_log_fault_policy parameter is set to allocate, is to attempt to replace any of the failed devices. Note, however, that there is no guarantee that the second stage will choose devices previously in-use by the mirror that had not been part of the failure if others are available.
For information on manually recovering from an LVM mirror failure, see 第 7.3 节 “修复 LVM 镜像错误”.
You can split off a redundant image of a mirrored logical volume to form a new logical volume. To split off an image, you use the --splitmirrors argument of the lvconvert command, specifying the number of redundant images to split off. You must use the --name argument of the command to specify a name for the newly-split-off logical volume.
The following command splits off a new logical volume named copy from the mirrored logical volume vg/lv. The new logical volume contains two mirror legs. In this example, LVM selects which devices to split off. 
# lvconvert --splitmirrors 2 --name copy vg/lv
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You can specify which devices to split off. The following command splits off a new logical volume named copy from the mirrored logical volume vg/lv. The new logical volume contains two mirror legs consisting of devices /dev/sdc1 and /dev/sde1. 
# lvconvert --splitmirrors 2 --name copy vg/lv /dev/sd[ce]1
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5.4.3.3. Repairing a Mirrored Logical Device
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You can use the lvconvert --repair command to repair a mirror after a disk failure. This brings the mirror back into a consistent state. The lvconvert --repair command is an interactive command that prompts you to indicate whether you want the system to attempt to replace any failed devices.
  • To skip the prompts and replace all of the failed devices, specify the -y option on the command line.
  • To skip the prompts and replace none of the failed devices, specify the -f option on the command line.
  • To skip the prompts and still indicate different replacement policies for the mirror image and the mirror log, you can specify the --use-policies argument to use the device replacement policies specified by the mirror_log_fault_policy and mirror_device_fault_policy parameters in the lvm.conf file.
5.4.3.4. 修改镜像卷配置
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You can increase or decrease the number of mirrors that a logical volume contains by using the lvconvert command. This allows you to convert a logical volume from a mirrored volume to a linear volume or from a linear volume to a mirrored volume. You can also use this command to reconfigure other mirror parameters of an existing logical volume, such as corelog.
When you convert a linear volume to a mirrored volume, you are creating mirror legs for an existing volume. This means that your volume group must contain the devices and space for the mirror legs and for the mirror log.
If you lose a leg of a mirror, LVM converts the volume to a linear volume so that you still have access to the volume, without the mirror redundancy. After you replace the leg, you can use the lvconvert command to restore the mirror. This procedure is provided in 第 7.3 节 “修复 LVM 镜像错误”.
The following command converts the linear logical volume vg00/lvol1 to a mirrored logical volume. 
# lvconvert -m1 vg00/lvol1
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The following command converts the mirrored logical volume vg00/lvol1 to a linear logical volume, removing the mirror leg. 
# lvconvert -m0 vg00/lvol1
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The following example adds an additional mirror leg to the existing logical volume vg00/lvol1. This example shows the configuration of the volume before and after the lvconvert command changed the volume to a volume with two mirror legs. 
# lvs -a -o name,copy_percent,devices vg00
  LV                  Copy%  Devices
  lvol1               100.00 lvol1_mimage_0(0),lvol1_mimage_1(0)
  [lvol1_mimage_0]        /dev/sda1(0)
  [lvol1_mimage_1]        /dev/sdb1(0)
  [lvol1_mlog]            /dev/sdd1(0)
# lvconvert -m 2 vg00/lvol1
  vg00/lvol1: Converted: 13.0%
  vg00/lvol1: Converted: 100.0%
  Logical volume lvol1 converted.
# lvs -a -o name,copy_percent,devices vg00
  LV                  Copy%  Devices
  lvol1               100.00 lvol1_mimage_0(0),lvol1_mimage_1(0),lvol1_mimage_2(0)
  [lvol1_mimage_0]        /dev/sda1(0)
  [lvol1_mimage_1]        /dev/sdb1(0)
  [lvol1_mimage_2]        /dev/sdc1(0)
  [lvol1_mlog]            /dev/sdd1(0)
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5.4.4. Creating Thinly-Provisioned Logical Volumes
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As of the Red Hat Enterprise Linux 6.4 release, logical volumes can be thinly provisioned. This allows you to create logical volumes that are larger than the available extents. Using thin provisioning, you can manage a storage pool of free space, known as a thin pool, which can be allocated to an arbitrary number of devices when needed by applications. You can then create devices that can be bound to the thin pool for later allocation when an application actually writes to the logical volume. The thin pool can be expanded dynamically when needed for cost-effective allocation of storage space.

注意

This section provides an overview of the basic commands you use to create and grow thinly-provisioned logical volumes. For detailed information on LVM thin provisioning as well as information on using the LVM commands and utilities with thinly-provisioned logical volumes, see the lvmthin(7) man page.

注意

Thin volumes are not supported across the nodes in a cluster. The thin pool and all its thin volumes must be exclusively activated on only one cluster node.
To create a thin volume, you perform the following tasks:
  1. Create a volume group with the vgcreate command.
  2. Create a thin pool with the lvcreate command.
  3. Create a thin volume in the thin pool with the lvcreate command.
You can use the -T (or --thin) option of the lvcreate command to create either a thin pool or a thin volume. You can also use -T option of the lvcreate command to create both a thin pool and a thin volume in that pool at the same time with a single command.
The following command uses the -T option of the lvcreate command to create a thin pool named mythinpool that is in the volume group vg001 and that is 100M in size. Note that since you are creating a pool of physical space, you must specify the size of the pool. The -T option of the lvcreate command does not take an argument; it deduces what type of device is to be created from the other options the command specifies. 
# lvcreate -L 100M -T vg001/mythinpool
  Rounding up size to full physical extent 4.00 MiB
  Logical volume "mythinpool" created
# lvs
  LV            VG     Attr     LSize   Pool Origin Data%  Move Log Copy% Convert
  my mythinpool vg001  twi-a-tz 100.00m               0.00
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The following command uses the -T option of the lvcreate command to create a thin volume named thinvolume in the thin pool vg001/mythinpool. Note that in this case you are specifying virtual size, and that you are specifying a virtual size for the volume that is greater than the pool that contains it. 
# lvcreate -V1G -T vg001/mythinpool -n thinvolume
  Logical volume "thinvolume" created
# lvs
  LV          VG       Attr     LSize   Pool       Origin Data%  Move Log Copy%  Convert
  mythinpool  vg001    twi-a-tz 100.00m                     0.00                        
  thinvolume  vg001    Vwi-a-tz   1.00g mythinpool          0.00
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The following command uses the -T option of the lvcreate command to create a thin pool and a thin volume in that pool by specifying both a size and a virtual size argument for the lvcreate command. This command creates a thin pool named mythinpool in the volume group vg001 and it also creates a thin volume named thinvolume in that pool. 
# lvcreate -L 100M -T vg001/mythinpool -V1G -n thinvolume
  Rounding up size to full physical extent 4.00 MiB
  Logical volume "thinvolume" created
# lvs
  LV           VG       Attr     LSize   Pool     Origin Data%  Move Log Copy%  Convert
  mythinpool   vg001    twi-a-tz 100.00m                   0.00                        
  thinvolume   vg001    Vwi-a-tz   1.00g mythinpool        0.00
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You can also create a thin pool by specifying the --thinpool parameter of the lvcreate command. Unlike the -T option, the --thinpool parameter requires an argument, which is the name of the thin pool logical volume that you are creating. The following example specifies the --thinpool parameter of the lvcreate command to create a thin pool named mythinpool that is in the volume group vg001 and that is 100M in size: 
# lvcreate -L 100M --thinpool mythinpool vg001
  Rounding up size to full physical extent 4.00 MiB
  Logical volume "mythinpool" created
# lvs
  LV          VG     Attr     LSize   Pool Origin Data%  Move Log Copy% Convert
  mythinpool  vg001  twi-a-tz 100.00m               0.00
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Striping is supported for pool creation. The following command creates a 100M thin pool named pool in volume group vg001 with two 64 kB stripes and a chunk size of 256 kB. It also creates a 1T thin volume, vg00/thin_lv. 
# lvcreate -i 2 -I 64 -c 256 -L100M -T vg00/pool -V 1T --name thin_lv
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You can extend the size of a thin volume with the lvextend command. You cannot, however, reduce the size of a thin pool.
The following command resizes an existing thin pool that is 100M in size by extending it another 100M. 
# lvextend -L+100M vg001/mythinpool
  Extending logical volume mythinpool to 200.00 MiB
  Logical volume mythinpool successfully resized
# lvs
  LV           VG       Attr     LSize   Pool     Origin Data%  Move Log Copy%  Convert
  mythinpool   vg001    twi-a-tz 200.00m                   0.00                        
  thinvolume   vg001    Vwi-a-tz   1.00g mythinpool          0.00
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As with other types of logical volumes, you can rename the volume with the lvrename, you can remove the volume with the lvremove, and you can display information about the volume with the lvs and lvdisplay commands.
By default, the lvcreate command sets the size of the thin pool's metadata logical volume according to the formula (Pool_LV_size / Pool_LV_chunk_size * 64). You cannot currently resize the metadata volume, however, so if you expect significant growth of the size of thin pool at a later time you should increase this value with the --poolmetadatasize parameter of the lvcreate command. The supported value for the thin pool's metadata logical volume is in the range between 2MiB and 16GiB.
You can use the --thinpool parameter of the lvconvert command to convert an existing logical volume to a thin pool volume. When you convert an existing logical volume to a thin pool volume, you must use the --poolmetadata parameter in conjunction with the --thinpool parameter of the lvconvert to convert an existing logical volume to the thin pool volume's metadata volume.

注意

Converting a logical volume to a thin pool volume or a thin pool metadata volume destroys the content of the logical volume, since in this case the lvconvert does not preserve the content of the devices but instead overwrites the content.
The following example converts the existing logical volume lv1 in volume group vg001 to a thin pool volume and converts the existing logical volume lv2 in volume group vg001 to the metadata volume for that thin pool volume. 
# lvconvert --thinpool vg001/lv1 --poolmetadata vg001/lv2
  Converted vg001/lv1 to thin pool.
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5.4.5. 创建快照卷
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注意

As of the Red Hat Enterprise Linux 6.4 release, LVM supports thinly-provisioned snapshots. For information on creating thinly provisioned snapshot volumes, see 第 5.4.6 节 “Creating Thinly-Provisioned Snapshot Volumes”.
Use the -s argument of the lvcreate command to create a snapshot volume. A snapshot volume is writable.

注意

LVM snapshots are not supported across the nodes in a cluster. You cannot create a snapshot volume in a clustered volume group. As of the Red Hat Enterprise Linux 6.1 release, however, if you need to create a consistent backup of data on a clustered logical volume you can activate the volume exclusively and then create the snapshot. For information on activating logical volumes exclusively on one node, see 第 5.7 节 “在群集的独立节点中激活逻辑卷”.

注意

As of the Red Hat Enterprise Linux 6.1 release, LVM snapshots are supported for mirrored logical volumes.
As of the Red Hat Enterprise Linux 6.3 release, snapshots are supported for RAID logical volumes. For information on RAID logical volumes, see 第 5.4.16 节 “RAID Logical Volumes”.
As of the Red Hat Enterprise Linux 6.5 release, LVM does not allow you to create a snapshot volume that is larger than the size of the origin volume plus needed metadata for the volume. If you specify a snapshot volume that is larger than this, the system will create a snapshot volume that is only as large as will be needed for the size of the origin.
By default, a snapshot volume is skipped during normal activation commands. For information on controlling the activation of a snapshot volume, see 第 5.4.17 节 “Controlling Logical Volume Activation”.
The following command creates a snapshot logical volume that is 100 MB in size named /dev/vg00/snap. This creates a snapshot of the origin logical volume named /dev/vg00/lvol1. If the original logical volume contains a file system, you can mount the snapshot logical volume on an arbitrary directory in order to access the contents of the file system to run a backup while the original file system continues to get updated. 
# lvcreate --size 100M --snapshot --name snap /dev/vg00/lvol1
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After you create a snapshot logical volume, specifying the origin volume on the lvdisplay command yields output that includes a list of all snapshot logical volumes and their status (active or inactive).
The following example shows the status of the logical volume /dev/new_vg/lvol0, for which a snapshot volume /dev/new_vg/newvgsnap has been created. 
# lvdisplay /dev/new_vg/lvol0
  --- Logical volume ---
  LV Name                /dev/new_vg/lvol0
  VG Name                new_vg
  LV UUID                LBy1Tz-sr23-OjsI-LT03-nHLC-y8XW-EhCl78
  LV Write Access        read/write
  LV snapshot status     source of
                         /dev/new_vg/newvgsnap1 [active]
  LV Status              available
  # open                 0
  LV Size                52.00 MB
  Current LE             13
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2
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The lvs command, by default, displays the origin volume and the current percentage of the snapshot volume being used for each snapshot volume. The following example shows the default output for the lvs command for a system that includes the logical volume /dev/new_vg/lvol0, for which a snapshot volume /dev/new_vg/newvgsnap has been created. 
# lvs
  LV         VG     Attr   LSize  Origin Snap%  Move Log Copy%
  lvol0      new_vg owi-a- 52.00M
  newvgsnap1 new_vg swi-a-  8.00M lvol0    0.20
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警告

因为快照在源卷有变化时会增大，所以常规使用 lvs 命令监控快照卷的比例以确定它还没有被填满是很重要的。使用了 100％ 的快照卷会完全丢失，因为写入源卷中不修改的部分的操作如果不破坏快照是无法成功的。
As of the Red Hat Enterprise Linux 6.2 release, there are two new features related to snapshots. First, in addition to the snapshot itself being invalidated when full, any mounted file systems on that snapshot device are forcibly unmounted, avoiding the inevitable file system errors upon access to the mount point. Second, you can specify the snapshot_autoextend_threshold option in the lvm.conf file. This option allows automatic extension of a snapshot whenever the remaining snapshot space drops below the threshold you set. This feature requires that there be unallocated space in the volume group.
As of the Red Hat Enterprise Linux 6.5 release, LVM does not allow you to create a snapshot volume that is larger than the size of the origin volume plus needed metadata for the volume. Similarly, automatic extension of a snapshot will not increase the size of a snapshot volume beyond the maximum calculated size that is necessary for the snapshot. Once a snapshot has grown large enough to cover the origin, it is no longer monitored for automatic extension.
Information on setting snapshot_autoextend_threshold and snapshot_autoextend_percent is provided in the lvm.conf file itself. For information about the lvm.conf file, see 附录 B, LVM 配置文件.

5.4.6. Creating Thinly-Provisioned Snapshot Volumes
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The Red Hat Enterprise Linux release 6.4 version of LVM provides support for thinly-provisioned snapshot volumes. For information on the benefits and limitations of thin snapshot volumes, see 第 3.3.7 节 “Thinly-Provisioned Snapshot Volumes”.

注意

This section provides an overview of the basic commands you use to create and grow thinly-provisioned snapshot volumes. For detailed information on LVM thin provisioning as well as information on using the LVM commands and utilities with thinly-provisioned logical volumes, see the lvmthin(7) man page.

重要

When creating a thin snapshot volume, you do not specify the size of the volume. If you specify a size parameter, the snapshot that will be created will not be a thin snapshot volume and will not use the thin pool for storing data. For example, the command lvcreate -s vg/thinvolume -L10M will not create a thin snapshot, even though the origin volume is a thin volume.
Thin snapshots can be created for thinly-provisioned origin volumes. As of the Red Hat Enterprise Linux 6.5 release, thin snapshots can also be created for origin volumes that are not thinly-provisioned.
You can specify a name for the snapshot volume with the --name option of the lvcreate command. It is recommended that you use this option when creating a logical volume so that you can more easily see the volume you have created when you display logical volumes with the lvs command.
The following command creates a thinly-provisioned snapshot volume of the thinly-provisioned logical volume vg001/thinvolume that is named mysnapshot1. 
# lvcreate -s --name mysnapshot1 vg001/thinvolume
  Logical volume "mysnapshot1" created
# lvs
  LV          VG       Attr     LSize   Pool       Origin     Data%  Move Log Copy%  Convert
  mysnapshot1 vg001    Vwi-a-tz   1.00g mythinpool thinvolume   0.00                        
  mythinpool  vg001    twi-a-tz 100.00m                         0.00                        
  thinvolume  vg001    Vwi-a-tz   1.00g mythinpool              0.00
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A thin snapshot volume has the same characteristics as any other thin volume. You can independently activate the volume, extend the volume, rename the volume, remove the volume, and even snapshot the volume.
By default, a snapshot volume is skipped during normal activation commands. For information on controlling the activation of a snapshot volume, see 第 5.4.17 节 “Controlling Logical Volume Activation”.
As of the Red Hat Enterprise Linux 6.5 release, you can create a thinly-provisioned snapshot of a non-thinly-provisioned logical volume. Since the non-thinly-provisioned logical volume is not contained within a thinpool, it is referred to as an external origin. External origin volumes can be used and shared by many thinly-provisioned snapshot volumes, even from different thin pools. The external origin must be inactive and read-only at the time the thinly-provisioned snapshot is created.
To create a thinly-provisioned snapshot of an external origin, you must specify the --thinpool option. The following command creates a thin snapshot volume of the read-only inactive volume origin_volume. The thin snapshot volume is named mythinsnap. The logical volume origin_volume then becomes the thin external origin for the thin shapshot volume mythinsnap in volume group vg001 that will use the existing thin pool vg001/pool. Because the origin volume must be in the same volume group as the snapshot volume, you do not need to specify the volume group when specifying the origin logical volume. 
# lvcreate -s --thinpool vg001/pool origin_volume --name mythinsnap
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You can create a second thinly-provisioned snapshot volume of the first snapshot volume, as in the following command. 
# lvcreate -s vg001/mythinsnap --name my2ndthinsnap
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5.4.7. Creating LVM Cache Logical Volumes
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As of the Red Hat Enterprise Linux 6.7 release, LVM provides full support for LVM cache logical volumes. A cache logical volume uses a small logical volume consisting of fast block devices (such as SSD drives) to improve the performance of a larger and slower logical volume by storing the frequently used blocks on the smaller, faster logical volume.
LVM caching uses the following LVM logical volume types. All of these associated logical volumes must be in the same volume group.
  • Origin logical volume — the large, slow logical volume
  • Cache pool logical volume — the small, fast logical volume, which is composed of two devices: the cache data logical volume, and the cache metadata logical volume
  • Cache data logical volume — the logical volume containing the data blocks for the cache pool logical volume
  • Cache metadata logical volume — the logical volume containing the metadata for the cache pool logical volume, which holds the accounting information that specifies where data blocks are stored (for example, on the origin logical volume or the cache data logical volume).
  • Cache logical volume — the logical volume containing the origin logical volume and the cache pool logical volume. This is the resultant usable device which encapsulates the various cache volume components.
The following procedure creates an LVM cache logical volume.
  1. Create a volume group that contains a slow physical volume and a fast physical volume. In this example. /dev/sde1 is a slow device and /dev/sdf1 is a fast device and both devices are contained in volume group VG. 
    # pvcreate /dev/sde1
# pvcreate /dev/sdf1
# vgcreate VG /dev/sde1 /dev/sdf1
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  2. Create the origin volume. This example creates an origin volume named lv that is 4G in size and that consists of /dev/sde1, the slow physical volume. 
    # lvcreate -L 4G -n lv VG /dev/sde1
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  3. Create the cache data logical volume. This logical volume will hold data blocks from the origin volume. The size of this logical volume is the size of the cache and will be reported as the size of the cache pool logical volume. This example creates the cache data volume named lv_cache. It is 2G in size and is contained on the fast device /dev/sdf1, which is part of the volume group VG. 
    # lvcreate -L 2G -n lv_cache VG /dev/sdf1
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  4. Create the cache metadata logical volume. This logical volume will hold cache pool metadata. The ratio of the size of the cache data logical volume to the size of the cache metadata logical volume should be about 1000:1, with a minimum size of 8MiB for the cache metadata logical volume. This example creates the cache metadata volume named lv_cache_meta. It is 12M in size and is also contained on the fast device /dev/sdf1, which is part of the volume group VG. 
    # lvcreate -L 12M -n lv_cache_meta VG /dev/sdf1
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  5. Create the cache pool logical volume by combining the cache data and the cache metadata logical volumes into a logical volume of type cache-pool. You can set the behavior of the cache pool in this step; in this example the cachemode argument is set to writethrough, which indicates that a write is considered complete only when it has been stored in both the cache pool logical volume and on the origin logical volume.
    When you execute this command, the cache data logical volume is renamed with _cdata appended to the original name of the cache data logical volume, and the cache metadata logical volume is renamed with _cmeta appended to the original name of the cache data logical volume; both of these volumes become hidden. 
    # lvconvert --type cache-pool --cachemode writethrough --poolmetadata VG/lv_cache_meta VG/lv_cache
  WARNING: Converting logical volume VG/lv_cache and VG/lv_cache_meta to pool's data and metadata volumes.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
  Converted VG/lv_cache to cache pool.
# lvs -a -o +devices
  LV               VG  Attr       LSize   Pool Origin Data%  Meta% Cpy%Sync Devices
  lv               VG  -wi-a-----   4.00g                                   /dev/sde1(0)
  lv_cache         VG  Cwi---C---   2.00g                                   lv_cache_cdata(0)
  [lv_cache_cdata] VG  Cwi-------   2.00g                                   /dev/sdf1(0)
  [lv_cache_cmeta] VG  ewi-------  12.00m                                   /dev/sdf1(512)
  [lvol0_pmspare]  VG  ewi-------  12.00m                                   /dev/sde1(1024)
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  6. Create the cache logical volume by combining the cache pool logical volume with the origin logical volume. The user-accessible cache logical volume takes the name of the origin logical volume. The origin logical volume becomes a hidden logical volume with _corig appended to the original name. You can execute this command when the origin logical volume is in use. 
    # lvconvert --type cache --cachepool VG/lv_cache VG/lv
  Logical volume VG/lv is now cached.
# lvs -a -o +devices
  LV                VG  Attr       LSize   Pool       Origin            Data%  Meta% Cpy%Sync Devices
  lv                VG  Cwi-a-C---   4.00g [lv_cache] [lv_corig] 0.02   2.31  0.00            lv_corig(0)
  [lv_corig]        VG  owi-aoC---   4.00g                                                    /dev/sde1(0)
  [lv_cache]        VG  Cwi---C---   2.00g                              0.02   2.31  0.00     lv_cache_cdata(0)
  [lv_cache_cdata]  VG  Cwi-ao----   2.00g                                                    /dev/sdf1(0)
  [lv_cache_cmeta]  VG  ewi-ao----  12.00m                                                    /dev/sdf1(512)
  [lvol0_pmspare]   VG  ewi-------  12.00m                                                    /dev/sde1(1024)
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For further information on LVM cache volumes, including additional administrative examples, see the lvmcache(7) man page.

5.4.8. Merging Snapshot Volumes
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As of the Red Hat Enterprise Linux 6 release, you can use the --merge option of the lvconvert command to merge a snapshot into its origin volume. If both the origin and snapshot volume are not open, the merge will start immediately. Otherwise, the merge will start the first time either the origin or snapshot are activated and both are closed. Merging a snapshot into an origin that cannot be closed, for example a root file system, is deferred until the next time the origin volume is activated. When merging starts, the resulting logical volume will have the origin’s name, minor number and UUID. While the merge is in progress, reads or writes to the origin appear as they were directed to the snapshot being merged. When the merge finishes, the merged snapshot is removed.
The following command merges snapshot volume vg00/lvol1_snap into its origin. 
# lvconvert --merge vg00/lvol1_snap
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You can specify multiple snapshots on the command line, or you can use LVM object tags to specify that multiple snapshots be merged to their respective origins. In the following example, logical volumes vg00/lvol1, vg00/lvol2, and vg00/lvol3 are all tagged with the tag @some_tag. The following command merges the snapshot logical volumes for all three volumes serially: vg00/lvol1, then vg00/lvol2, then vg00/lvol3. If the --background option were used, all snapshot logical volume merges would start in parallel. 
# lvconvert --merge @some_tag
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For information on tagging LVM objects, see 附录 D, LVM 对象标签. For further information on the lvconvert --merge command, see the lvconvert(8) man page.

5.4.9. 持久的设备号码
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在载入模块的时候会自动分配主、副设备号码。如果总是用相同的设备（主和副）号码激活块设备，可使有些应用程序获得最佳性能。您可以通过使用以下参数来指定 lvcreate 和 lvchange 来达到此目的： 
--persistent y --major major --minor minor
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Use a large minor number to be sure that it has not already been allocated to another device dynamically.
如果您使用 NFS 导出一个文件系统，在导出文件中指定 fsid 参数可避免在 LVM 中设定持久的设备号码。

5.4.10. 修改逻辑卷组的参数
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要修改逻辑卷参数，请使用 lvchange 命令。有关您可以修改的参数列表，请参考 lvchange(8) man page。
You can use the lvchange command to activate and deactivate logical volumes. To activate and deactivate all the logical volumes in a volume group at the same time, use the vgchange command, as described in 第 5.3.8 节 “修改卷组参数”.
The following command changes the permission on volume lvol1 in volume group vg00 to be read-only. 
# lvchange -pr vg00/lvol1
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5.4.11. 重新命名逻辑卷
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要重新命名一个现有逻辑卷，请使用 lvrename 命令。
Either of the following commands renames logical volume lvold in volume group vg02 to lvnew. 
# lvrename /dev/vg02/lvold /dev/vg02/lvnew
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# lvrename vg02 lvold lvnew
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Renaming the root logical volume requires additional reconfiguration. For information on renaming a root volume, see How to rename root volume group or logical volume in Red Hat Enterprise Linux.
For more information on activating logical volumes on individual nodes in a cluster, see 第 5.7 节 “在群集的独立节点中激活逻辑卷”.

5.4.12. 删除逻辑卷
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To remove an inactive logical volume, use the lvremove command. If the logical volume is currently mounted, unmount the volume before removing it. In addition, in a clustered environment you must deactivate a logical volume before it can be removed.
The following command removes the logical volume /dev/testvg/testlv from the volume group testvg. Note that in this case the logical volume has not been deactivated. 
# lvremove /dev/testvg/testlv
Do you really want to remove active logical volume "testlv"? [y/n]: y
  Logical volume "testlv" successfully removed
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您可以使用 lvchange -an 命令在删除逻辑卷之前明确将其失活，这样就不会出现询问您是否删除某个激活逻辑卷的提示。

5.4.13. 显示逻辑卷
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有三个命令可显示 LVM 逻辑卷的属性：lvs、lvdisplay 和 lvscan。
The lvs command provides logical volume information in a configurable form, displaying one line per logical volume. The lvs command provides a great deal of format control, and is useful for scripting. For information on using the lvs command to customize your output, see 第 5.8 节 “为 LVM 自定义报告”.
lvdisplay 命令用混合格式显示物理属性（大小、布局和映射）。
The following command shows the attributes of lvol2 in vg00. If snapshot logical volumes have been created for this original logical volume, this command shows a list of all snapshot logical volumes and their status (active or inactive) as well. 
# lvdisplay -v /dev/vg00/lvol2
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lvscan 命令扫描系统中所有逻辑卷并将其列出，如下: 
# lvscan
 ACTIVE                   '/dev/vg0/gfslv' [1.46 GB] inherit
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5.4.14. 增大逻辑卷
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要增大逻辑卷的大小，请使用 lvextend 命令。
当您扩展逻辑卷时，您可以指定您想要增大的量，或者在您扩展它之后，它应该是多大。
下面的命令将逻辑卷 /dev/myvg/homevol 增大到 12GB。 
# lvextend -L12G /dev/myvg/homevol 
lvextend -- extending logical volume "/dev/myvg/homevol" to 12 GB
lvextend -- doing automatic backup of volume group "myvg"
lvextend -- logical volume "/dev/myvg/homevol" successfully extended
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下面的命令为逻辑卷 /dev/myvg/homevol 添加了另一个 GB。 
# lvextend -L+1G /dev/myvg/homevol
lvextend -- extending logical volume "/dev/myvg/homevol" to 13 GB
lvextend -- doing automatic backup of volume group "myvg"
lvextend -- logical volume "/dev/myvg/homevol" successfully extended
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As with the lvcreate command, you can use the -l argument of the lvextend command to specify the number of extents by which to increase the size of the logical volume. You can also use this argument to specify a percentage of the volume group, or a percentage of the remaining free space in the volume group. The following command extends the logical volume called testlv to fill all of the unallocated space in the volume group myvg. 
# lvextend -l +100%FREE /dev/myvg/testlv
  Extending logical volume testlv to 68.59 GB
  Logical volume testlv successfully resized
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在您扩展完逻辑卷后，有必要增大文件系统的大小与之进行匹配。
在默认情况下，大多数重新定义文件系统大小的工具都会将文件系统的大小增加到基本逻辑卷的大小，这样您就不必担心为两个命令指定相同的容量了。
5.4.14.1. 扩展条状卷
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要增加条状逻辑卷的大小，基本物理卷中必须有足够的可用空间，以便让卷组支持它。例如，如果您有一个使用了这个卷组的双向条带，那么在卷组中添加一个物理卷将会使您无法扩展条带，反之，您必须在卷组中添加至少两个物理卷。
For example, consider a volume group vg that consists of two underlying physical volumes, as displayed with the following vgs command. 
# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     2   0   0 wz--n- 271.31G 271.31G
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您可以使用整个卷组空间创建一个条带。 
# lvcreate -n stripe1 -L 271.31G -i 2 vg
  Using default stripesize 64.00 KB
  Rounding up size to full physical extent 271.31 GB
  Logical volume "stripe1" created
# lvs -a -o +devices
  LV      VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe1 vg   -wi-a- 271.31G                               /dev/sda1(0),/dev/sdb1(0)
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注意：那个卷组中已经没有剩余空间了。 
# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     2   1   0 wz--n- 271.31G    0
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下面的命令在卷组中添加了另一个物理卷，那么就有了 135G 的额外空间。 
# vgextend vg /dev/sdc1
  Volume group "vg" successfully extended
# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     3   1   0 wz--n- 406.97G 135.66G
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此时您不能扩展条状逻辑卷来充满卷组，因为需要两个基本设备来将数据按条状保存。 
# lvextend vg/stripe1 -L 406G
  Using stripesize of last segment 64.00 KB
  Extending logical volume stripe1 to 406.00 GB
  Insufficient suitable allocatable extents for logical volume stripe1: 34480 
more required
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To extend the striped logical volume, add another physical volume and then extend the logical volume. In this example, having added two physical volumes to the volume group we can extend the logical volume to the full size of the volume group. 
# vgextend vg /dev/sdd1
  Volume group "vg" successfully extended
# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     4   1   0 wz--n- 542.62G 271.31G
# lvextend vg/stripe1 -L 542G
  Using stripesize of last segment 64.00 KB
  Extending logical volume stripe1 to 542.00 GB
  Logical volume stripe1 successfully resized
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如果您没有足够的基本物理设备来扩展条状逻辑卷，那么在扩展不是条状的情况下也可能扩大卷，但可能导致性能不平衡。当为逻辑卷添加空间时，默认操作是使用与现有逻辑卷最新片段相同的条状参数，但您可覆盖那些参数。下面的例子是在启动 lvextend 命令失败后，使用剩余的可用空间扩大了条状逻辑卷。 
# lvextend vg/stripe1 -L 406G
  Using stripesize of last segment 64.00 KB
  Extending logical volume stripe1 to 406.00 GB
  Insufficient suitable allocatable extents for logical volume stripe1: 34480 
more required
# lvextend -i1 -l+100%FREE vg/stripe1
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5.4.14.2. Extending a Mirrored Volume
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As of the Red Hat Enterprise Linux 6.3 release, it is possible to grow mirrored logical volumes with the lvextend command without performing a synchronization of the new mirror regions.
If you specify the --nosync option when you create a mirrored logical volume with the lvcreate command, the mirror regions are not synchronized when the mirror is created, as described in 第 5.4.3 节 “创建镜像卷”. If you later extend a mirror that you have created with the --nosync option, the mirror extensions are not synchronized at that time, either.
You can determine whether an existing logical volume was created with the --nosync option by using the lvs command to display the volume's attributes. A logical volume will have an attribute bit 1 of "M" if it is a mirrored volume that was created without an initial synchronization, and it will have an attribute bit 1 of "m" if it was created with initial synchronization.
The following command displays the attributes of a mirrored logical volume named lv that was created without initial synchronization, showing attribute bit 1 as "M". Attribute bit 7 is "m", indicating a target type of mirror. For information on the meaning of the attribute bits, see 表 5.4 “lvs 显示字段”. 
# lvs vg
  LV   VG   Attr     LSize Pool Origin Snap%  Move Log     Copy%  Convert
  lv   vg   Mwi-a-m- 5.00g                         lv_mlog 100.00
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If you grow this mirrored logical volume with the lvextend command, the mirror extension will not be resynchronized.
If you created a mirrored logical volume without specifying the --nosync option of the lvcreate command, you can grow the logical volume without resynchronizing the mirror by specifying the --nosync option of the lvextend command.
The following example extends a logical volume that was created without the --nosync option, indicated that the mirror was synchronized when it was created. This example, however, specifies that the mirror not be synchronized when the volume is extended. Note that the volume has an attribute of "m", but after executing the lvextend commmand with the --nosync option the volume has an attribute of "M". 
# lvs vg
  LV   VG   Attr     LSize  Pool Origin Snap%  Move Log     Copy%  Convert
  lv   vg   mwi-a-m- 20.00m                         lv_mlog 100.00        
# lvextend -L +5G vg/lv --nosync
  Extending 2 mirror images.
  Extending logical volume lv to 5.02 GiB
  Logical volume lv successfully resized
# lvs vg
  LV   VG   Attr     LSize Pool Origin Snap%  Move Log     Copy%  Convert
  lv   vg   Mwi-a-m- 5.02g                         lv_mlog 100.00
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If a mirror is inactive, it will not automatically skip synchronization when you extend the mirror, even if you create the mirror with the --nosync option specified. Instead, you will be prompted whether to do a full resync of the extended portion of the logical volume.

注意

If a mirror is performing recovery, you cannot extend the mirrored logical volume if you created or extended the volume with the --nosync option specified. If you did not specify the --nosync option, however, you can extend the mirror while it is recovering.
When extending an LVM volume, you can use the --alloc cling option of the lvextend command to specify the cling allocation policy. This policy will choose space on the same physical volumes as the last segment of the existing logical volume. If there is insufficient space on the physical volumes and a list of tags is defined in the lvm.conf file, LVM will check whether any of the tags are attached to the physical volumes and seek to match those physical volume tags between existing extents and new extents.
For example, if you have logical volumes that are mirrored between two sites within a single volume group, you can tag the physical volumes according to where they are situated by tagging the physical volumes with @site1 and @site2 tags and specify the following line in the lvm.conf file: 
cling_tag_list = [ "@site1", "@site2" ]
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For information on tagging physical volumes, see 附录 D, LVM 对象标签.
In the following example, the lvm.conf file has been modified to contain the following line: 
cling_tag_list = [ "@A", "@B" ]
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Also in this example, a volume group taft has been created that consists of the physical volumes /dev/sdb1, /dev/sdc1, /dev/sdd1, /dev/sde1, /dev/sdf1, /dev/sdg1, and /dev/sdh1. These physical volumes have been tagged with tags A, B, and C. The example does not use the C tag, but this will show that LVM uses the tags to select which physical volumes to use for the mirror legs. 
# pvs -a -o +pv_tags /dev/sd[bcdefgh]1
  PV         VG   Fmt  Attr PSize   PFree   PV Tags
  /dev/sdb1  taft lvm2 a-   135.66g 135.66g A
  /dev/sdc1  taft lvm2 a-   135.66g 135.66g B
  /dev/sdd1  taft lvm2 a-   135.66g 135.66g B
  /dev/sde1  taft lvm2 a-   135.66g 135.66g C
  /dev/sdf1  taft lvm2 a-   135.66g 135.66g C
  /dev/sdg1  taft lvm2 a-   135.66g 135.66g A
  /dev/sdh1  taft lvm2 a-   135.66g 135.66g A
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The following command creates a 100GB mirrored volume from the volume group taft. 
# lvcreate -m 1 -n mirror --nosync -L 100G taft
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The following command shows which devices are used for the mirror legs and mirror log. 
# lvs -a -o +devices
  LV                VG        Attr   LSize   Log         Copy%  Devices
  mirror            taft      Mwi-a- 100.00g mirror_mlog 100.00
mirror_mimage_0(0),mirror_mimage_1(0)
  [mirror_mimage_0] taft      iwi-ao 100.00g                    /dev/sdb1(0)
  [mirror_mimage_1] taft      iwi-ao 100.00g                    /dev/sdc1(0)
  [mirror_mlog]     taft      lwi-ao   4.00m                    /dev/sdh1(0)
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The following command extends the size of the mirrored volume, using the cling allocation policy to indicate that the mirror legs should be extended using physical volumes with the same tag. 
# lvextend --alloc cling -L +100G taft/mirror
  Extending 2 mirror images.
  Extending logical volume mirror to 200.00 GiB
  Logical volume mirror successfully resized
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The following display command shows that the mirror legs have been extended using physical volumes with the same tag as the leg. Note that the physical volumes with a tag of C were ignored. 
# lvs -a -o +devices
  LV                VG        Attr   LSize   Log         Copy%  Devices
  mirror            taft      Mwi-a- 200.00g mirror_mlog  50.16
mirror_mimage_0(0),mirror_mimage_1(0)
  [mirror_mimage_0] taft      Iwi-ao 200.00g                    /dev/sdb1(0)
  [mirror_mimage_0] taft      Iwi-ao 200.00g                    /dev/sdg1(0)
  [mirror_mimage_1] taft      Iwi-ao 200.00g                    /dev/sdc1(0)
  [mirror_mimage_1] taft      Iwi-ao 200.00g                    /dev/sdd1(0)
  [mirror_mlog]     taft      lwi-ao   4.00m                    /dev/sdh1(0)
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5.4.15. 缩小逻辑卷
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You can reduce the size of a logical volume with the lvreduce command.

注意

Shrinking is not supported on a GFS2 or XFS file system, so you cannot reduce the size of a logical volume that contains a GFS2 or XFS file system.
If the logical volume you are reducing contains a file system, to prevent data loss you must ensure that the file system is not using the space in the logical volume that is being reduced. For this reason, it is recommended that you use the --resizefs option of the lvreduce command when the logical volume contains a file system. When you use this option, the lvreduce command attempts to reduce the file system before shrinking the logical volume. If shrinking the file sytem fails, as can occur if the file system is full or the file system does not support shrinking, then the lvreduce command will fail and not attempt to shrink the logical volume.

警告

In most cases, the lvreduce command warns about possible data loss and asks for a confirmation. However, you should not rely on these confirmation prompts to prevent data loss because in some cases you will not see these prompts, such as when the logical volume is inactive or the --resizefs option is not used.
Note that using the --test option of the lvreduce command does not indicate where the operation is safe, as this option does not check the file system or test the file system resize.
The following command shrinks the logical volume lvol1 in volume group vg00 to be 64 megabytes. In this example, lvol1 contains a file system, which this command resizes together with the logical volume. This example shows the output to the command. 
# lvreduce --resizefs -L 64M vg00/lvol1
fsck from util-linux 2.23.2
/dev/mapper/vg00-lvol1: clean, 11/25688 files, 8896/102400 blocks
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/mapper/vg00-lvol1 to 65536 (1k) blocks.
The filesystem on /dev/mapper/vg00-lvol1 is now 65536 blocks long.

  Size of logical volume vg00/lvol1 changed from 100.00 MiB (25 extents) to 64.00 MiB (16 extents).
  Logical volume vg00/lvol1 successfully resized.
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Specifying the - sign before the resize value indicates that the value will be subtracted from the logical volume's actual size. The following example shows the command you would use if, instead of shrinking a logical volume to an absolute size of 64 megabytes, you wanted to shrink the volume by a value 64 megabytes. 
# lvreduce --resizefs -L -64M vg00/lvol1
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5.4.16. RAID Logical Volumes
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As of the Red Hat Enterprise Linux 6.3 release, LVM supports RAID4/5/6 and a new implementation of mirroring. The latest implementation of mirroring differs from the previous implementation of mirroring (documented in 第 5.4.3 节 “创建镜像卷”) in the following ways:
  • The segment type for the new implementation of mirroring is raid1. For the earlier implementation, the segment type is mirror.
  • The new implementation of mirroring leverages MD software RAID, just as for the RAID 4/5/6 implementations.
  • The new implementation of mirroring maintains a fully redundant bitmap area for each mirror image, which increases its fault handling capabilities. This means that there is no --mirrorlog option or --corelog option for mirrors created with this segment type.
  • The new implementation of mirroring can handle transient failures.
  • Mirror images can be temporarily split from the array and merged back into the array later.
  • The new implementation of mirroring supports snapshots (as do the higher-level RAID implementations).
  • The new RAID implementations are not cluster-aware. You cannot create an LVM RAID logical volume in a clustered volume group.
For information on how failures are handled by the RAID logical volumes, see 第 5.4.16.8 节 “Setting a RAID fault policy”.
The remainder of this section describes the following administrative tasks you can perform on LVM RAID devices:
5.4.16.1. Creating a RAID Logical Volume
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To create a RAID logical volume, you specify a raid type as the --type argument of the lvcreate command. Usually when you create a logical volume with the lvcreate command, the --type argument is implicit. For example, when you specify the -i stripes argument, the lvcreate command assumes the --type stripe option. When you specify the -m mirrors argument, the lvcreate command assumes the --type mirror option. When you create a RAID logical volume, however, you must explicitly specify the segment type you desire. The possible RAID segment types are described in 表 5.1 “RAID Segment Types”.
Expand
表 5.1. RAID Segment Types
Segment type描述
raid1 RAID1 mirroring
raid4 RAID4 dedicated parity disk
raid5 Same as raid5_ls
raid5_la
RAID5 left asymmetric.
Rotating parity 0 with data continuation
raid5_ra
RAID5 right asymmetric.
Rotating parity N with data continuation
raid5_ls
RAID5 left symmetric.
Rotating parity 0 with data restart
raid5_rs
RAID5 right symmetric.
Rotating parity N with data restart
raid6 Same as raid6_zr
raid6_zr
RAID6 zero restart
Rotating parity zero (left-to-right) with data restart
raid6_nr
RAID6 N restart
Rotating parity N (left-to-right) with data restart
raid6_nc
RAID6 N continue
Rotating parity N (left-to-right) with data continuation
raid10 (Red Hat Enterprise Linux 6.4 and later
Striped mirrors
Striping of mirror sets
For most users, specifying one of the five available primary types (raid1, raid4, raid5, raid6, raid10) should be sufficient. For more information on the different algorithms used by RAID 5/6, see chapter four of the Common RAID Disk Data Format Specification at http://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf.
When you create a RAID logical volume, LVM creates a metadata subvolume that is one extent in size for every data or parity subvolume in the array. For example, creating a 2-way RAID1 array results in two metadata subvolumes (lv_rmeta_0 and lv_rmeta_1) and two data subvolumes (lv_rimage_0 and lv_rimage_1). Similarly, creating a 3-way stripe (plus 1 implicit parity device) RAID4 results in 4 metadata subvolumes (lv_rmeta_0, lv_rmeta_1, lv_rmeta_2, and lv_rmeta_3) and 4 data subvolumes (lv_rimage_0, lv_rimage_1, lv_rimage_2, and lv_rimage_3).
The following command creates a 2-way RAID1 array named my_lv in the volume group my_vg that is 1G in size. 
# lvcreate --type raid1 -m 1 -L 1G -n my_lv my_vg
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You can create RAID1 arrays with different numbers of copies according to the value you specify for the -m argument. Although the -m argument is the same argument used to specify the number of copies for the previous mirror implementation, in this case you override the default segment type mirror by explicitly setting the segment type as raid1. Similarly, you specify the number of stripes for a RAID 4/5/6 logical volume with the familiar -i argument, overriding the default segment type with the desired RAID type. You can also specify the stripe size with the -I argument.

注意

You can set the default mirror segment type to raid1 by changing mirror_segtype_default in the lvm.conf file.
The following command creates a RAID5 array (3 stripes + 1 implicit parity drive) named my_lv in the volume group my_vg that is 1G in size. Note that you specify the number of stripes just as you do for an LVM striped volume; the correct number of parity drives is added automatically. 
# lvcreate --type raid5 -i 3 -L 1G -n my_lv my_vg
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The following command creates a RAID6 array (3 stripes + 2 implicit parity drives) named my_lv in the volume group my_vg that is 1G in size. 
# lvcreate --type raid6 -i 3 -L 1G -n my_lv my_vg
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After you have created a RAID logical volume with LVM, you can activate, change, remove, display, and use the volume just as you would any other LVM logical volume.
When you create RAID10 logical volumes, the background I/O required to initialize the logical volumes with a sync operation can crowd out other I/O operations to LVM devices, such as updates to volume group metadata, particularly when you are creating many RAID logical volumes. This can cause the other LVM operations to slow down.
As of Red Hat Enterprise Linux 6.5, you can control the rate at which a RAID logical volume is initialized by implementing recovery throttling. You control the rate at which sync operations are performed by setting the minimum and maximum I/O rate for those operations with the --minrecoveryrate and --maxrecoveryrate options of the lvcreate command. You specify these options as follows.
  • --maxrecoveryrate Rate[bBsSkKmMgG]
    Sets the maximum recovery rate for a RAID logical volume so that it will not crowd out nominal I/O operations. The Rate is specified as an amount per second for each device in the array. If no suffix is given, then kiB/sec/device is assumed. Setting the recovery rate to 0 means it will be unbounded.
  • --minrecoveryrate Rate[bBsSkKmMgG]
    Sets the minimum recovery rate for a RAID logical volume to ensure that I/O for sync operations achieves a minimum throughput, even when heavy nominal I/O is present. The Rate is specified as an amount per second for each device in the array. If no suffix is given, then kiB/sec/device is assumed.
The following command creates a 2-way RAID10 array with 3 stripes that is 10G is size with a maximum recovery rate of 128 kiB/sec/device. The array is named my_lv and is in the volume group my_vg. 
lvcreate --type raid10 -i 2 -m 1 -L 10G --maxrecoveryrate 128 -n my_lv my_vg
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You can also specify minimum and maximum recovery rates for a RAID scrubbing operation. For information on RAID scrubbing, see 第 5.4.16.10 节 “Scrubbing a RAID Logical Volume”.
5.4.16.2. Converting a Linear Device to a RAID Device
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You can convert an existing linear logical volume to a RAID device by using the --type argument of the lvconvert command.
The following command converts the linear logical volume my_lv in volume group my_vg to a 2-way RAID1 array. 
# lvconvert --type raid1 -m 1 my_vg/my_lv
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Since RAID logical volumes are composed of metadata and data subvolume pairs, when you convert a linear device to a RAID1 array, a new metadata subvolume is created and associated with the original logical volume on (one of) the same physical volumes that the linear volume is on. The additional images are added in metadata/data subvolume pairs. For example, if the original device is as follows: 
# lvs -a -o name,copy_percent,devices my_vg
  LV     Copy%  Devices     
  my_lv         /dev/sde1(0)
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After conversion to a 2-way RAID1 array the device contains the following data and metadata subvolume pairs: 
# lvconvert --type raid1 -m 1 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            6.25   my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(0)                 
  [my_lv_rimage_1]        /dev/sdf1(1)                 
  [my_lv_rmeta_0]         /dev/sde1(256)               
  [my_lv_rmeta_1]         /dev/sdf1(0)
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If the metadata image that pairs with the original logical volume cannot be placed on the same physical volume, the lvconvert will fail.
You can convert an existing RAID1 LVM logical volume to an LVM linear logical volume with the lvconvert command by specifying the -m0 argument. This removes all the RAID data subvolumes and all the RAID metadata subvolumes that make up the RAID array, leaving the top-level RAID1 image as the linear logical volume.
The following example displays an existing LVM RAID1 logical volume. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(1)                 
  [my_lv_rimage_1]        /dev/sdf1(1)                 
  [my_lv_rmeta_0]         /dev/sde1(0)                 
  [my_lv_rmeta_1]         /dev/sdf1(0)
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The following command converts the LVM RAID1 logical volume my_vg/my_lv to an LVM linear device. 
# lvconvert -m0 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV      Copy%  Devices     
  my_lv          /dev/sde1(1)
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When you convert an LVM RAID1 logical volume to an LVM linear volume, you can specify which physical volumes to remove. The following example shows the layout of an LVM RAID1 logical volume made up of two images: /dev/sda1 and /dev/sdb1. In this example, the lvconvert command specifies that you want to remove /dev/sda1, leaving /dev/sdb1 as the physical volume that makes up the linear device. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdb1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdb1(0)
# lvconvert -m0 my_vg/my_lv /dev/sda1
# lvs -a -o name,copy_percent,devices my_vg
  LV    Copy%  Devices
  my_lv        /dev/sdb1(1)
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You can convert an existing mirrored LVM device to a RAID1 LVM device with the lvconvert command by specifying the --type raid1 argument. This renames the mirror subvolumes (*_mimage_*) to RAID subvolumes (*_rimage_*). In addition, the mirror log is removed and metadata subvolumes (*_rmeta_*) are created for the data subvolumes on the same physical volumes as the corresponding data subvolumes.
The following example shows the layout of a mirrored logical volume my_vg/my_lv. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv             15.20 my_lv_mimage_0(0),my_lv_mimage_1(0)
  [my_lv_mimage_0]        /dev/sde1(0)                 
  [my_lv_mimage_1]        /dev/sdf1(0)                 
  [my_lv_mlog]            /dev/sdd1(0)
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The following command converts the mirrored logical volume my_vg/my_lv to a RAID1 logical volume. 
# lvconvert --type raid1 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(0)                 
  [my_lv_rimage_1]        /dev/sdf1(0)                 
  [my_lv_rmeta_0]         /dev/sde1(125)               
  [my_lv_rmeta_1]         /dev/sdf1(125)
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You can change the number of images in an existing RAID1 array just as you can change the number of images in the earlier implementation of LVM mirroring, by using the lvconvert command to specify the number of additional metadata/data subvolume pairs to add or remove. For information on changing the volume configuration in the earlier implementation of LVM mirroring, see 第 5.4.3.4 节 “修改镜像卷配置”.
When you add images to a RAID1 device with the lvconvert command, you can specify the total number of images for the resulting device, or you can specify how many images to add to the device. You can also optionally specify on which physical volumes the new metadata/data image pairs will reside.
Metadata subvolumes (named *_rmeta_*) always exist on the same physical devices as their data subvolume counterparts *_rimage_*). The metadata/data subvolume pairs will not be created on the same physical volumes as those from another metadata/data subvolume pair in the RAID array (unless you specify --alloc anywhere).
The format for the command to add images to a RAID1 volume is as follows: 
lvconvert -m new_absolute_count vg/lv [removable_PVs]
lvconvert -m +num_additional_images vg/lv [removable_PVs]
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For example, the following display shows the LVM device my_vg/my_lv which is a 2-way RAID1 array: 
# lvs -a -o name,copy_percent,devices my_vg
  LV            Copy%  Devices                      
  my_lv                 6.25 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(0)                 
  [my_lv_rimage_1]        /dev/sdf1(1)                 
  [my_lv_rmeta_0]         /dev/sde1(256)               
  [my_lv_rmeta_1]         /dev/sdf1(0)
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The following command converts the 2-way RAID1 device my_vg/my_lv to a 3-way RAID1 device: 
# lvconvert -m 2 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv              6.25 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sde1(0)                                
  [my_lv_rimage_1]        /dev/sdf1(1)                                
  [my_lv_rimage_2]        /dev/sdg1(1)                                
  [my_lv_rmeta_0]         /dev/sde1(256)                              
  [my_lv_rmeta_1]         /dev/sdf1(0)                                
  [my_lv_rmeta_2]         /dev/sdg1(0)
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When you add an image to a RAID1 array, you can specify which physical volumes to use for the image. The following command converts the 2-way RAID1 device my_vg/my_lv to a 3-way RAID1 device, specifying that the physical volume /dev/sdd1 be used for the array: 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv             56.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdb1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdb1(0)
# lvconvert -m 2 my_vg/my_lv /dev/sdd1
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv             28.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdb1(1)
  [my_lv_rimage_2]        /dev/sdd1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdb1(0)
  [my_lv_rmeta_2]         /dev/sdd1(0)
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To remove images from a RAID1 array, use the following command. When you remove images from a RAID1 device with the lvconvert command, you can specify the total number of images for the resulting device, or you can specify how many images to remove from the device. You can also optionally specify the physical volumes from which to remove the device. 
lvconvert -m new_absolute_count vg/lv [removable_PVs]
lvconvert -m -num_fewer_images vg/lv [removable_PVs]
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Additionally, when an image and its associated metadata subvolume volume are removed, any higher-numbered images will be shifted down to fill the slot. If you remove lv_rimage_1 from a 3-way RAID1 array that consists of lv_rimage_0, lv_rimage_1, and lv_rimage_2, this results in a RAID1 array that consists of lv_rimage_0 and lv_rimage_1. The subvolume lv_rimage_2 will be renamed and take over the empty slot, becoming lv_rimage_1.
The following example shows the layout of a 3-way RAID1 logical volume my_vg/my_lv. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sde1(1)                                
  [my_lv_rimage_1]        /dev/sdf1(1)                                
  [my_lv_rimage_2]        /dev/sdg1(1)                                
  [my_lv_rmeta_0]         /dev/sde1(0)                                
  [my_lv_rmeta_1]         /dev/sdf1(0)                                
  [my_lv_rmeta_2]         /dev/sdg1(0)
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The following command converts the 3-way RAID1 logical volume into a 2-way RAID1 logical volume. 
# lvconvert -m1 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(1)                 
  [my_lv_rimage_1]        /dev/sdf1(1)                 
  [my_lv_rmeta_0]         /dev/sde1(0)                 
  [my_lv_rmeta_1]         /dev/sdf1(0)
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The following command converts the 3-way RAID1 logical volume into a 2-way RAID1 logical volume, specifying the physical volume that contains the image to remove as /dev/sde1. 
# lvconvert -m1 my_vg/my_lv /dev/sde1
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sdf1(1)                 
  [my_lv_rimage_1]        /dev/sdg1(1)                 
  [my_lv_rmeta_0]         /dev/sdf1(0)                 
  [my_lv_rmeta_1]         /dev/sdg1(0)
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You can split off an image of a RAID logical volume to form a new logical volume. The procedure for splitting off a RAID image is the same as the procedure for splitting off a redundant image of a mirrored logical volume, as described in 第 5.4.3.2 节 “Splitting Off a Redundant Image of a Mirrored Logical Volume”.
The format of the command to split off a RAID image is as follows: 
lvconvert --splitmirrors count -n splitname vg/lv [removable_PVs]
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Just as when you are removing a RAID images from an existing RAID1 logical volume (as described in 第 5.4.16.5 节 “Changing the Number of Images in an Existing RAID1 Device”), when you remove a RAID data subvolume (and its associated metadata subvolume) from the middle of the device, any higher numbered images will be shifted down to fill the slot. The index numbers on the logical volumes that make up a RAID array will thus be an unbroken sequence of integers.

注意

You cannot split off a RAID image if the RAID1 array is not yet in sync.
The following example splits a 2-way RAID1 logical volume, my_lv, into two linear logical volumes, my_lv and new. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv             12.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(1)                 
  [my_lv_rimage_1]        /dev/sdf1(1)                 
  [my_lv_rmeta_0]         /dev/sde1(0)                 
  [my_lv_rmeta_1]         /dev/sdf1(0)                 
# lvconvert --splitmirror 1 -n new my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV      Copy%  Devices     
  my_lv          /dev/sde1(1)
  new            /dev/sdf1(1)
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The following example splits a 3-way RAID1 logical volume, my_lv, into a 2-way RAID1 logical volume, my_lv, and a linear logical volume, new 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sde1(1)                                
  [my_lv_rimage_1]        /dev/sdf1(1)                                
  [my_lv_rimage_2]        /dev/sdg1(1)                                
  [my_lv_rmeta_0]         /dev/sde1(0)                                
  [my_lv_rmeta_1]         /dev/sdf1(0)                                
  [my_lv_rmeta_2]         /dev/sdg1(0)                                
# lvconvert --splitmirror 1 -n new my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV            Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sde1(1)                 
  [my_lv_rimage_1]        /dev/sdf1(1)                 
  [my_lv_rmeta_0]         /dev/sde1(0)                 
  [my_lv_rmeta_1]         /dev/sdf1(0)                 
  new                     /dev/sdg1(1)
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5.4.16.7. Splitting and Merging a RAID Image
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You can temporarily split off an image of a RAID1 array for read-only use while keeping track of any changes by using the --trackchanges argument in conjunction with the --splitmirrors argument of the lvconvert command. This allows you to merge the image back into the array at a later time while resyncing only those portions of the array that have changed since the image was split.
The format for the lvconvert command to split off a RAID image is as follows. 
lvconvert --splitmirrors count --trackchanges vg/lv [removable_PVs]
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When you split off a RAID image with the --trackchanges argument, you can specify which image to split but you cannot change the name of the volume being split. In addition, the resulting volumes have the following constraints.
  • The new volume you create is read-only.
  • You cannot resize the new volume.
  • You cannot rename the remaining array.
  • You cannot resize the remaining array.
  • You can activate the new volume and the remaining array independently.
You can merge an image that was split off with the --trackchanges argument specified by executing a subsequent lvconvert command with the --merge argument. When you merge the image, only the portions of the array that have changed since the image was split are resynced.
The format for the lvconvert command to merge a RAID image is as follows. 
lvconvert --merge raid_image
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The following example creates a RAID1 logical volume and then splits off an image from that volume while tracking changes to the remaining array. 
# lvcreate --type raid1 -m2 -L1G -n my_lv .vg
  Logical volume "my_lv" created
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sdb1(1)                                
  [my_lv_rimage_1]        /dev/sdc1(1)                                
  [my_lv_rimage_2]        /dev/sdd1(1)                                
  [my_lv_rmeta_0]         /dev/sdb1(0)                                
  [my_lv_rmeta_1]         /dev/sdc1(0)                                
  [my_lv_rmeta_2]         /dev/sdd1(0)                                
# lvconvert --splitmirrors 1 --trackchanges my_vg/my_lv
  my_lv_rimage_2 split from my_lv for read-only purposes.
  Use 'lvconvert --merge my_vg/my_lv_rimage_2' to merge back into my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sdb1(1)                                
  [my_lv_rimage_1]        /dev/sdc1(1)                                
  my_lv_rimage_2         /dev/sdd1(1)                                
  [my_lv_rmeta_0]         /dev/sdb1(0)                                
  [my_lv_rmeta_1]         /dev/sdc1(0)                                
  [my_lv_rmeta_2]         /dev/sdd1(0)
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The following example splits off an image from a RAID1 volume while tracking changes to the remaining array, then merges the volume back into the array. 
# lvconvert --splitmirrors 1 --trackchanges my_vg/my_lv
  lv_rimage_1 split from my_lv for read-only purposes.
  Use 'lvconvert --merge my_vg/my_lv_rimage_1' to merge back into my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sdc1(1)                 
  my_lv_rimage_1          /dev/sdd1(1)                 
  [my_lv_rmeta_0]         /dev/sdc1(0)                 
  [my_lv_rmeta_1]         /dev/sdd1(0)                 
# lvconvert --merge my_vg/my_lv_rimage_1
  my_vg/my_lv_rimage_1 successfully merged back into my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sdc1(1)                 
  [my_lv_rimage_1]        /dev/sdd1(1)                 
  [my_lv_rmeta_0]         /dev/sdc1(0)                 
  [my_lv_rmeta_1]         /dev/sdd1(0)
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Once you have split off an image from a RAID1 volume, you can make the split permanent by issuing a second lvconvert --splitmirrors command, repeating the initial lvconvert command that split the image without specifying the --trackchanges argument. This breaks the link that the --trackchanges argument created.
After you have split an image with the --trackchanges argument, you cannot issue a subsequent lvconvert --splitmirrors command on that array unless your intent is to permanently split the image being tracked.
The following sequence of commands splits an image and tracks the image and then permanently splits off the image being tracked. 
# lvconvert --splitmirrors 1 --trackchanges my_vg/my_lv
  my_lv_rimage_1 split from my_lv for read-only purposes.
  Use 'lvconvert --merge my_vg/my_lv_rimage_1' to merge back into my_lv
# lvconvert --splitmirrors 1 -n new my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV   Copy%  Devices     
  my_lv          /dev/sdc1(1)
  new            /dev/sdd1(1)
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Note, however, that the following sequence of commands will fail. 
# lvconvert --splitmirrors 1 --trackchanges my_vg/my_lv
  my_lv_rimage_1 split from my_lv for read-only purposes.
  Use 'lvconvert --merge my_vg/my_lv_rimage_1' to merge back into my_lv
# lvconvert --splitmirrors 1 --trackchanges my_vg/my_lv
  Cannot track more than one split image at a time
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Similarly, the following sequence of commands will fail as well, since the split image is not the image being tracked. 
# lvconvert --splitmirrors 1 --trackchanges my_vg/my_lv
  my_lv_rimage_1 split from my_lv for read-only purposes.
  Use 'lvconvert --merge my_vg/my_lv_rimage_1' to merge back into my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                      
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sdc1(1)                 
  my_lv_rimage_1          /dev/sdd1(1)                 
  [my_lv_rmeta_0]         /dev/sdc1(0)                 
  [my_lv_rmeta_1]         /dev/sdd1(0)                 
# lvconvert --splitmirrors 1 -n new my_vg/my_lv /dev/sdc1
  Unable to split additional image from my_lv while tracking changes for my_lv_rimage_1
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5.4.16.8. Setting a RAID fault policy
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LVM RAID handles device failures in an automatic fashion based on the preferences defined by the raid_fault_policy field in the lvm.conf file.
  • If the raid_fault_policy field is set to allocate, the system will attempt to replace the failed device with a spare device from the volume group. If there is no available spare device, this will be reported to the system log.
  • If the raid_fault_policy field is set to warn, the system will produce a warning and the log will indicate that a device has failed. This allows the user to determine the course of action to take.
As long as there are enough devices remaining to support usability, the RAID logical volume will continue to operate.
5.4.16.8.1. The allocate RAID Fault Policy
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In the following example, the raid_fault_policy field has been set to allocate in the lvm.conf file. The RAID logical volume is laid out as follows. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sde1(1)                                
  [my_lv_rimage_1]        /dev/sdf1(1)                                
  [my_lv_rimage_2]        /dev/sdg1(1)                                
  [my_lv_rmeta_0]         /dev/sde1(0)                                
  [my_lv_rmeta_1]         /dev/sdf1(0)                                
  [my_lv_rmeta_2]         /dev/sdg1(0)
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If the /dev/sde device fails, the system log will display error messages. 
# grep lvm /var/log/messages 
Jan 17 15:57:18 bp-01 lvm[8599]: Device #0 of raid1 array, my_vg-my_lv, has failed.
Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at
250994294784: Input/output error
Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at
250994376704: Input/output error
Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at 0:
Input/output error
Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at
4096: Input/output error
Jan 17 15:57:19 bp-01 lvm[8599]: Couldn't find device with uuid
3lugiV-3eSP-AFAR-sdrP-H20O-wM2M-qdMANy.
Jan 17 15:57:27 bp-01 lvm[8599]: raid1 array, my_vg-my_lv, is not in-sync.
Jan 17 15:57:36 bp-01 lvm[8599]: raid1 array, my_vg-my_lv, is now in-sync.
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Since the raid_fault_policy field has been set to allocate, the failed device is replaced with a new device from the volume group. 
# lvs -a -o name,copy_percent,devices vg
  Couldn't find device with uuid 3lugiV-3eSP-AFAR-sdrP-H20O-wM2M-qdMANy.
  LV            Copy%  Devices                                     
  lv            100.00 lv_rimage_0(0),lv_rimage_1(0),lv_rimage_2(0)
  [lv_rimage_0]        /dev/sdh1(1)                                
  [lv_rimage_1]        /dev/sdf1(1)                                
  [lv_rimage_2]        /dev/sdg1(1)                                
  [lv_rmeta_0]         /dev/sdh1(0)                                
  [lv_rmeta_1]         /dev/sdf1(0)                                
  [lv_rmeta_2]         /dev/sdg1(0)
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Note that even though the failed device has been replaced, the display still indicates that LVM could not find the failed device. This is because, although the failed device has been removed from the RAID logical volume, the failed device has not yet been removed from the volume group. To remove the failed device from the volume group, you can execute vgreduce --removemissing VG.
If the raid_fault_policy has been set to allocate but there are no spare devices, the allocation will fail, leaving the logical volume as it is. If the allocation fails, you have the option of fixing the drive, then deactivating and activating the logical volume, as described in 第 5.4.16.8.2 节 “The warn RAID Fault Policy”. Alternately, you can replace the failed device, as described in 第 5.4.16.9 节 “Replacing a RAID device”.
5.4.16.8.2. The warn RAID Fault Policy
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In the following example, the raid_fault_policy field has been set to warn in the lvm.conf file. The RAID logical volume is laid out as follows. 
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sdh1(1)                                
  [my_lv_rimage_1]        /dev/sdf1(1)                                
  [my_lv_rimage_2]        /dev/sdg1(1)                                
  [my_lv_rmeta_0]         /dev/sdh1(0)                                
  [my_lv_rmeta_1]         /dev/sdf1(0)                                
  [my_lv_rmeta_2]         /dev/sdg1(0)
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If the /dev/sdh device fails, the system log will display error messages. In this case, however, LVM will not automatically attempt to repair the RAID device by replacing one of the images. Instead, if the device has failed you can replace the device with the --repair argument of the lvconvert command, as shown below. 
# lvconvert --repair my_vg/my_lv
  /dev/sdh1: read failed after 0 of 2048 at 250994294784: Input/output error
  /dev/sdh1: read failed after 0 of 2048 at 250994376704: Input/output error
  /dev/sdh1: read failed after 0 of 2048 at 0: Input/output error
  /dev/sdh1: read failed after 0 of 2048 at 4096: Input/output error
  Couldn't find device with uuid fbI0YO-GX7x-firU-Vy5o-vzwx-vAKZ-feRxfF.
Attempt to replace failed RAID images (requires full device resync)? [y/n]: y

# lvs -a -o name,copy_percent,devices my_vg
  Couldn't find device with uuid fbI0YO-GX7x-firU-Vy5o-vzwx-vAKZ-feRxfF.
  LV               Copy%  Devices                                     
  my_lv             64.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sde1(1)                                
  [my_lv_rimage_1]        /dev/sdf1(1)                                
  [my_lv_rimage_2]        /dev/sdg1(1)                                
  [my_lv_rmeta_0]         /dev/sde1(0)                                
  [my_lv_rmeta_1]         /dev/sdf1(0)                                
  [my_lv_rmeta_2]         /dev/sdg1(0)
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Note that even though the failed device has been replaced, the display still indicates that LVM could not find the failed device. This is because, although the failed device has been removed from the RAID logical volume, the failed device has not yet been removed from the volume group. To remove the failed device from the volume group, you can execute vgreduce --removemissing VG.
If the device failure is a transient failure or you are able to repair the device that failed, as of Red Hat Enterprise Linux release 6.5 you can initiate recovery of the failed device with the --refresh option of the lvchange command. Previously it was necessary to deactivate and then activate the logical volume.
The following command refreshes a logical volume. 
# lvchange --refresh my_vg/my_lv
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5.4.16.9. Replacing a RAID device
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RAID is not like traditional LVM mirroring. LVM mirroring required failed devices to be removed or the mirrored logical volume would hang. RAID arrays can keep on running with failed devices. In fact, for RAID types other than RAID1, removing a device would mean converting to a lower level RAID (for example, from RAID6 to RAID5, or from RAID4 or RAID5 to RAID0). Therefore, rather than removing a failed device unconditionally and potentially allocating a replacement, LVM allows you to replace a device in a RAID volume in a one-step solution by using the --replace argument of the lvconvert command.
The format for the lvconvert --replace is as follows. 
lvconvert --replace dev_to_remove vg/lv [possible_replacements]
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The following example creates a RAID1 logical volume and then replaces a device in that volume. 
# lvcreate --type raid1 -m2 -L 1G -n my_lv my_vg
  Logical volume "my_lv" created
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sdb1(1)                                
  [my_lv_rimage_1]        /dev/sdb2(1)                                
  [my_lv_rimage_2]        /dev/sdc1(1)                                
  [my_lv_rmeta_0]         /dev/sdb1(0)                                
  [my_lv_rmeta_1]         /dev/sdb2(0)                                
  [my_lv_rmeta_2]         /dev/sdc1(0)                                
# lvconvert --replace /dev/sdb2 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices                                     
  my_lv             37.50 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sdb1(1)                                
  [my_lv_rimage_1]        /dev/sdc2(1)                                
  [my_lv_rimage_2]        /dev/sdc1(1)                                
  [my_lv_rmeta_0]         /dev/sdb1(0)                                
  [my_lv_rmeta_1]         /dev/sdc2(0)                                
  [my_lv_rmeta_2]         /dev/sdc1(0)
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The following example creates a RAID1 logical volume and then replaces a device in that volume, specifying which physical volume to use for the replacement. 
# lvcreate --type raid1 -m1 -L 100 -n my_lv my_vg
  Logical volume "my_lv" created
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdb1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdb1(0)
# pvs
  PV          VG       Fmt  Attr PSize    PFree
  /dev/sda1   my_vg    lvm2 a--  1020.00m  916.00m
  /dev/sdb1   my_vg    lvm2 a--  1020.00m  916.00m
  /dev/sdc1   my_vg    lvm2 a--  1020.00m 1020.00m
  /dev/sdd1   my_vg    lvm2 a--  1020.00m 1020.00m
# lvconvert --replace /dev/sdb1 my_vg/my_lv /dev/sdd1
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv             28.00 my_lv_rimage_0(0),my_lv_rimage_1(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdd1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdd1(0)
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You can replace more than one RAID device at a time by specifying multiple replace arguments, as in the following example. 
# lvcreate --type raid1 -m 2 -L 100 -n my_lv my_vg
  Logical volume "my_lv" created
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv            100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdb1(1)
  [my_lv_rimage_2]        /dev/sdc1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdb1(0)
  [my_lv_rmeta_2]         /dev/sdc1(0)
# lvconvert --replace /dev/sdb1 --replace /dev/sdc1 my_vg/my_lv
# lvs -a -o name,copy_percent,devices my_vg
  LV               Copy%  Devices
  my_lv             60.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
  [my_lv_rimage_0]        /dev/sda1(1)
  [my_lv_rimage_1]        /dev/sdd1(1)
  [my_lv_rimage_2]        /dev/sde1(1)
  [my_lv_rmeta_0]         /dev/sda1(0)
  [my_lv_rmeta_1]         /dev/sdd1(0)
  [my_lv_rmeta_2]         /dev/sde1(0)
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注意

When you specify a replacement drive using the lvconvert --replace command, the replacement drives should never be allocated from extra space on drives already used in the array. For example, lv_rimage_0 and lv_rimage_1 should not be located on the same physical volume.
5.4.16.10. Scrubbing a RAID Logical Volume
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As of the Red Hat Enterprise Linux 6.5 release, LVM provides scrubbing support for RAID logical volumes. RAID scrubbing is the process of reading all the data and parity blocks in an array and checking to see whether they are coherent.
You initiate a RAID scrubbing operation with the --syncaction option of the lvchange command. You specify either a check or repair operation. A check operation goes over the array and records the number of discrepancies in the array but does not repair them. A repair operation corrects the discrepancies as it finds them.
The format of the command to scrub a RAID logical volume is as follows: 
lvchange --syncaction {check|repair} vg/raid_lv
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注意

The lvchange --syncaction repair vg/raid_lv operation does not perform the same function as the lvconvert --repair vg/raid_lv operation. The lvchange --syncaction repair operation initiates a background synchronization operation on the array, while the lvconvert --repair operation is designed to repair/replace failed devices in a mirror or RAID logical volume.
In support of the new RAID scrubbing operation, the lvs command now supports two new printable fields: raid_sync_action and raid_mismatch_count. These fields are not printed by default. To display these fields you specify them with the -o parameter of the lvs, as follows. 
lvs -o +raid_sync_action,raid_mismatch_count vg/lv
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The raid_sync_action field displays the current synchronization operation that the raid volume is performing. It can be one of the following values:
  • idle: All sync operations complete (doing nothing)
  • resync: Initializing an array or recovering after a machine failure
  • recover: Replacing a device in the array
  • check: Looking for array inconsistencies
  • repair: Looking for and repairing inconsistencies
The raid_mismatch_count field displays the number of discrepancies found during a check operation.
The Cpy%Sync field of the lvs command now prints the progress of any of the raid_sync_action operations, including check and repair.
The lv_attr field of the lvs display now provides additional indicators in support of the RAID scrubbing operation. Bit 9 of this field displays the health of the logical volume, and it now supports the following indicators.
  • (m)ismatches indicates that there are discrepancies in a RAID logical volume. This character is shown after a scrubbing operation has detected that portions of the RAID are not coherent.
  • (r)efresh indicates that a device in a RAID array has suffered a failure and the kernel regards it as failed, even though LVM can read the device label and considers the device to be operational. The logical should be (r)efreshed to notify the kernel that the device is now available, or the device should be (r)eplaced if it is suspected of having failed.
For information on the lvs command, see 第 5.8.2 节 “对象选择”.
When you perform a RAID scrubbing operation, the background I/O required by the sync operations can crowd out other I/O operations to LVM devices, such as updates to volume group metadata. This can cause the other LVM operations to slow down. You can control the rate at which the RAID logical volume is scrubbed by implementing recovery throttling.
You control the rate at which sync operations are performed by setting the minimum and maximum I/O rate for those operations with the --minrecoveryrate and --maxrecoveryrate options of the lvchange command. You specify these options as follows.
  • --maxrecoveryrate Rate[bBsSkKmMgG]
    Sets the maximum recovery rate for a RAID logical volume so that it will not crowd out nominal I/O operations. The Rate is specified as an amount per second for each device in the array. If no suffix is given, then kiB/sec/device is assumed. Setting the recovery rate to 0 means it will be unbounded.
  • --minrecoveryrate Rate[bBsSkKmMgG]
    Sets the minimum recovery rate for a RAID logical volume to ensure that I/O for sync operations achieves a minimum throughput, even when heavy nominal I/O is present. The Rate is specified as an amount per second for each device in the array. If no suffix is given, then kiB/sec/device is assumed.
As of the Red Hat Enterprise Linux release 6.5, you can control the I/O operations for a device in a RAID1 logical volume by using the --writemostly and --writebehind parameters of the lvchange command. The format for using these parameters is as follows.
  • --[raid]writemostly PhysicalVolume[:{t|y|n}]
    Marks a device in a RAID1 logical volume as write-mostly. All reads to these drives will be avoided unless necessary. Setting this parameter keeps the number of I/O operations to the drive to a minimum. The default behavior is to set the write-mostly attribute for the specified physical volume in the logical volume. It is possible to remove the write-mostly flag by appending :n to the physical volume or to toggle the value by specifying :t. The --writemostly argument can be specified more than one time in a single command, making it possible to toggle the write-mostly attributes for all the physical volumes in a logical volume at once.
  • --[raid]writebehind IOCount
    Specifies the maximum number of outstanding writes that are allowed to devices in a RAID1 logical volume that are marked as write-mostly. Once this value is exceeded, writes become synchronous, causing all writes to the constituent devices to complete before the array signals the write has completed. Setting the value to zero clears the preference and allows the system to choose the value arbitrarily.

5.4.17. Controlling Logical Volume Activation
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You can flag a logical volume to be skipped during normal activation commands with the -k or --setactivationskip {y|n} option of the lvcreate or lvchange command. This flag is not applied during deactivation.
You can determine whether this flag is set for a logical volume with the lvs command, which displays the k attribute as in the following example. 
# lvs vg/thin1s1
LV         VG  Attr       LSize Pool  Origin
thin1s1    vg  Vwi---tz-k 1.00t pool0 thin1
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By default, thin snapshot volumes are flagged for activation skip. You can activate a logical volume with the k attribute set by using the -K or --ignoreactivationskip option in addition to the standard -ay or --activate y option.
The following command activates a thin snapshot logical volume. 
# lvchange -ay -K VG/SnapLV
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The persistent "activation skip" flag can be turned off when the logical volume is created by specifying the -kn or --setactivationskip n option of the lvcreate command. You can turn the flag off for an existing logical volume by specifying the -kn or --setactivationskip n option of the lvchange command. You can turn the flag on again with the -ky or --setactivationskip y option.
The following command creates a snapshot logical volume without the activation skip flag 
# lvcreate --type thin -n SnapLV -kn -s ThinLV --thinpool VG/ThinPoolLV
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The following command removes the activation skip flag from a snapshot logical volume. 
# lvchange -kn VG/SnapLV
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You can control the default activation skip setting with the auto_set_activation_skip setting in the /etc/lvm/lvm.conf file.

5.5. 用过滤器控制 LVM 设备扫描
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At startup, the vgscan command is run to scan the block devices on the system looking for LVM labels, to determine which of them are physical volumes and to read the metadata and build up a list of volume groups. The names of the physical volumes are stored in the LVM cache file of each node in the system, /etc/lvm/cache/.cache. Subsequent commands may read that file to avoiding rescanning.
You can control which devices LVM scans by setting up filters in the lvm.conf configuration file. The filters in the lvm.conf file consist of a series of simple regular expressions that get applied to the device names that are in the /dev directory to decide whether to accept or reject each block device found.
The following examples show the use of filters to control which devices LVM scans. Note that some of these examples do not necessarily represent best practice, as the regular expressions are matched freely against the complete pathname. For example, a/loop/ is equivalent to a/.*loop.*/ and would match /dev/solooperation/lvol1.
下面的过滤器添加所有找到的设备，这是配置文件中没有配置过滤器的默认行为： 
filter = [ "a/.*/" ]
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下面的过滤器会删除光驱以避免在驱动器中没有介质时造成延迟： 
filter = [ "r|/dev/cdrom|" ]
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下面的过滤器添加所有回路设备并删除其它块设备： 
filter = [ "a/loop.*/", "r/.*/" ]
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下面的过滤器添加所有回路设备和 IDE 设备，同时删除所有其它块设备： 
filter =[ "a|loop.*|", "a|/dev/hd.*|", "r|.*|" ]
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下面的过滤器只添加第一个 IDE 驱动器中的分区 8，同时删除所有其它块设备： 
filter = [ "a|^/dev/hda8$|", "r/.*/" ]
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注意

When the lvmetad daemon is running, the filter = setting in the /etc/lvm/lvm.conf file does not apply when you execute the pvscan --cache device command. To filter devices, you need to use the global_filter = setting. Devices that fail the global filter are not opened by LVM and are never scanned. You may need to use a global filter, for example, when you use LVM devices in VMs and you do not want the contents of the devices in the VMs to be scanned by the physical host.
For more information on the lvm.conf file, see 附录 B, LVM 配置文件 and the lvm.conf(5) man page.

5.6. 在线数据重定位
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您可以使用 pvmove 命令在系统还在使用时移动数据。
pvmove 命令将数据分成片段，并生成临时镜像来移动每个片段。有关 pvmove 命令操作的详细内容请参考 pvmove(8) man page。

注意

In order to perform a pvmove operation in a cluster, you should ensure that the cmirror package is installed and the cmirrord service is running.
下面的命令将物理卷 /dev/sdc1 中所有分配了的空间都移动到卷组中其它可用物理卷中： 
# pvmove /dev/sdc1
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The following command moves just the extents of the logical volume MyLV. 
# pvmove -n MyLV /dev/sdc1
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Since the pvmove command can take a long time to execute, you may want to run the command in the background to avoid display of progress updates in the foreground. The following command moves all extents allocated to the physical volume /dev/sdc1 over to /dev/sdf1 in the background. 
# pvmove -b /dev/sdc1 /dev/sdf1
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下面的命令以 5 秒为间隔，以百分比形式报告移动的过程。 
# pvmove -i5 /dev/sdd1
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5.7. 在群集的独立节点中激活逻辑卷
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If you have LVM installed in a cluster environment, you may at times need to activate logical volumes exclusively on one node.
要在一个节点上完全激活逻辑卷，请使用 lvchange -aey 命令。另外，您可以使用 lvchange -aly 来只激活本地节点中的逻辑卷，而不是所有逻辑卷。您可以晚些时候在附加节点上同时激活它们。
You can also activate logical volumes on individual nodes by using LVM tags, which are described in 附录 D, LVM 对象标签. You can also specify activation of nodes in the configuration file, which is described in 附录 B, LVM 配置文件.

5.8. 为 LVM 自定义报告
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您可以使用 pvs、lvs 和 vgs 命令得到一份 LVM 对象的简洁自定义报告。这些命令生成的报告包括每行一个对象的输出结果。每行包含有关对象属性字段排序列表。选择要报告的对象有五种方法：根据物理卷、卷组、逻辑卷、物理卷片段和逻辑卷片段。
以下部分提供了：
  • 您可以用来扩展生成报告格式的参数概述。
  • 您可以为每个 LVM 对象选择的字段列表。
  • 您可以用来对生成的报告进行排序的命令参数总结。
  • 指定报告输出结果单位的步骤。

5.8.1. 格式控制
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无论您使用 pvs、lvs 或者 vgs 命令，都要确定默认字段显示和排列顺序。您可以使用以下参数来控制这些命令的输出结果：
  • You can change what fields are displayed to something other than the default by using the -o argument. For example, the following output is the default display for the pvs command (which displays information about physical volumes). 
    # pvs
  PV         VG     Fmt  Attr PSize  PFree
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G
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    您可以用下面的命令只显示物理卷的名称和大小。 
    # pvs -o pv_name,pv_size
  PV         PSize
  /dev/sdb1  17.14G
  /dev/sdc1  17.14G
  /dev/sdd1  17.14G
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  • 您可以用 (+) 符号在输出结果中附加一个字段，它通常与 -o 参数合用。
    下面的例子除默认字段外还显示物理卷 UUID。 
    # pvs -o +pv_uuid
  PV         VG     Fmt  Attr PSize  PFree  PV UUID
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G onFF2w-1fLC-ughJ-D9eB-M7iv-6XqA-dqGeXY
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G Joqlch-yWSj-kuEn-IdwM-01S9-X08M-mcpsVe
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G yvfvZK-Cf31-j75k-dECm-0RZ3-0dGW-UqkCS
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  • 在命令中添加 -v 参数使其包括一些额外的字段。例如：pvs -v 命令将在默认字段之外显示 DevSize 和 PV UUID 字段。 
    # pvs -v
    Scanning for physical volume names
  PV         VG     Fmt  Attr PSize  PFree  DevSize PV UUID
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G  17.14G onFF2w-1fLC-ughJ-D9eB-M7iv-6XqA-dqGeXY
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G  17.14G Joqlch-yWSj-kuEn-IdwM-01S9-XO8M-mcpsVe
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G  17.14G yvfvZK-Cf31-j75k-dECm-0RZ3-0dGW-tUqkCS
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  • --noheadings 参数制止标题行。这在写脚本时很有用。
    下面的命令合并使用 --noheadings 和 pv_name 参数，将生成所有物理卷的列表。 
    # pvs --noheadings -o pv_name
  /dev/sdb1
  /dev/sdc1
  /dev/sdd1
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  • The --separator separator argument uses separator to separate each field.
    下面的例子使用等号（＝）分隔 pvs 命令的默认输出字段。 
    # pvs --separator =
  PV=VG=Fmt=Attr=PSize=PFree
  /dev/sdb1=new_vg=lvm2=a-=17.14G=17.14G
  /dev/sdc1=new_vg=lvm2=a-=17.14G=17.09G
  /dev/sdd1=new_vg=lvm2=a-=17.14G=17.14G
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    要在使用 separator 参数时让字段对齐，请联合使用 separator 和 --aligned 参数。 
    # pvs --separator = --aligned
  PV        =VG    =Fmt =Attr=PSize =PFree
  /dev/sdb1 =new_vg=lvm2=a-  =17.14G=17.14G
  /dev/sdc1 =new_vg=lvm2=a-  =17.14G=17.09G
  /dev/sdd1 =new_vg=lvm2=a-  =17.14G=17.14G
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You can use the -P argument of the lvs or vgs command to display information about a failed volume that would otherwise not appear in the output. For information on the output this argument yields, see 第 7.2 节 “在失败的设备中显示信息。”.
有关显示参数的完整列表请参考 pvs(8)、vgs(8) 和 lvs(8) man page。
卷组字段可以与物理卷（和物理卷片段）字段或者逻辑卷（和逻辑卷片段）字段混合，但物理卷和逻辑卷字段不能混合。例如：下面的命令将在输出结果中每行显示一个物理卷。 
# vgs -o +pv_name
  VG     #PV #LV #SN Attr   VSize  VFree  PV
  new_vg   3   1   0 wz--n- 51.42G 51.37G /dev/sdc1
  new_vg   3   1   0 wz--n- 51.42G 51.37G /dev/sdd1
  new_vg   3   1   0 wz--n- 51.42G 51.37G /dev/sdb1
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5.8.2. 对象选择
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这部分提供了一组列表，表中列出的有关 LVM 对象的信息您可以用 pvs、vgs 和 lvs 命令获得。
为方便起见，字段名称前缀如果与命令默认字段匹配就可以去掉。例如：在 pvs 命令中，name 的指的是 pv_name，但使用 vgs 命令时，name 被理解为 vg_name。
执行以下命令和执行 pvs -o pv_free 的结果相同。 
# pvs -o free
  PFree
  17.14G
  17.09G
  17.14G
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注意

The number of characters in the attribute fields in pvs, vgs, and lvs output may increase in later releases. The existing character fields will not change position, but new fields may be added to the end. You should take this into account when writing scripts that search for particular attribute characters, searching for the character based on its relative position to the beginning of the field, but not for its relative position to the end of the field. For example, to search for the character p in the ninth bit of the lv_attr field, you could search for the string "^/........p/", but you should not search for the string "/*p$/".
pvs 命令
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表 5.2 “pvs 显示字段” lists the display arguments of the pvs command, along with the field name as it appears in the header display and a description of the field.
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表 5.2. pvs 显示字段
参数标题描述
dev_sizeDevSize创建物理卷的基本设备的大小
pe_start1st PE在基本设备中调整到第一个物理扩展的起始位置
pv_attrAttr物理卷状态：可分配（a）或者导出的（x）。
pv_fmtFmt The metadata format of the physical volume (lvm2 or lvm1)
pv_freePFree物理卷中剩余的可用空间
pv_namePV 物理卷名称
pv_pe_alloc_countAlloc已经使用的物理扩展数目
pv_pe_countPE 物理扩展数量
pvseg_sizeSSize物理卷的片段大小
pvseg_startStart物理卷片段的起始物理扩展
pv_sizePSize物理卷的大小
pv_tagsPV Tags附加到物理卷的 LVM 标签
pv_usedUsed目前物理卷中已经使用的空间量
pv_uuidPV UUID物理卷的 UUID
默认情况下 pvs 命令显示以下字段：pv_name、vg_name、pv_fmt、pv_attr、pv_size、pv_free。结果根据 pv_name 排序。 
# pvs
  PV         VG     Fmt  Attr PSize  PFree
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.13G
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使用带 -v 参数的 pvs 命令向默认显示中添加以下字段：dev_size、pv_uuid。 
# pvs -v
    Scanning for physical volume names
  PV         VG     Fmt  Attr PSize  PFree  DevSize PV UUID
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G  17.14G onFF2w-1fLC-ughJ-D9eB-M7iv-6XqA-dqGeXY
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G  17.14G Joqlch-yWSj-kuEn-IdwM-01S9-XO8M-mcpsVe
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.13G  17.14G yvfvZK-Cf31-j75k-dECm-0RZ3-0dGW-tUqkCS
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您可以使用 pvs 命令的 --segments 参数显示每个物理卷片段的信息。一个片段就是一组扩展。查看片段在想要查看逻辑卷是否有很多碎片时很有用。
pvs --segments 命令默认显示以下字段：pv_name、vg_name、pv_fmt、pv_attr、pv_size、pv_free、pvseg_start、pvseg_size。结果按照物理卷中 pv_name 和 pvseg_size 排序。 
# pvs --segments
  PV         VG         Fmt  Attr PSize  PFree  Start SSize
  /dev/hda2  VolGroup00 lvm2 a-   37.16G 32.00M     0  1172
  /dev/hda2  VolGroup00 lvm2 a-   37.16G 32.00M  1172    16
  /dev/hda2  VolGroup00 lvm2 a-   37.16G 32.00M  1188     1
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G     0    26
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G    26    24
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G    50    26
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G    76    24
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G   100    26
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G   126    24
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G   150    22
  /dev/sda1  vg         lvm2 a-   17.14G 16.75G   172  4217
  /dev/sdb1  vg         lvm2 a-   17.14G 17.14G     0  4389
  /dev/sdc1  vg         lvm2 a-   17.14G 17.14G     0  4389
  /dev/sdd1  vg         lvm2 a-   17.14G 17.14G     0  4389
  /dev/sde1  vg         lvm2 a-   17.14G 17.14G     0  4389
  /dev/sdf1  vg         lvm2 a-   17.14G 17.14G     0  4389
  /dev/sdg1  vg         lvm2 a-   17.14G 17.14G     0  4389
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您可以使用 pvs -a 查看被 LVM 侦测出来但还没有初始化为 LVM 物理卷的设备。 
# pvs -a
  PV                             VG     Fmt  Attr PSize  PFree
  /dev/VolGroup00/LogVol01                   --       0      0
  /dev/new_vg/lvol0                          --       0      0
  /dev/ram                                   --       0      0
  /dev/ram0                                  --       0      0
  /dev/ram2                                  --       0      0
  /dev/ram3                                  --       0      0
  /dev/ram4                                  --       0      0
  /dev/ram5                                  --       0      0
  /dev/ram6                                  --       0      0
  /dev/root                                  --       0      0
  /dev/sda                                   --       0      0
  /dev/sdb                                   --       0      0
  /dev/sdb1                      new_vg lvm2 a-   17.14G 17.14G
  /dev/sdc                                   --       0      0
  /dev/sdc1                      new_vg lvm2 a-   17.14G 17.09G
  /dev/sdd                                   --       0      0
  /dev/sdd1                      new_vg lvm2 a-   17.14G 17.14G
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vgs 命令
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表 5.3 “vgs 显示字段” lists the display arguments of the vgs command, along with the field name as it appears in the header display and a description of the field.
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表 5.3. vgs 显示字段
参数标题描述
lv_count#LV 卷组中含有的逻辑卷数目
max_lvMaxLV卷组中最多可用逻辑卷数量（如果没有限制就是 0）
max_pvMaxPV卷组中最多允许的物理卷数目（如果没有限制就是 0）
pv_count#PV 定义卷组的物理卷数目
snap_count#SN 卷组包含的快照数目
vg_attrAttr卷组状态：可写入（w）、只读（r）、可重新定义大小（z）、导出的（x）、不完整的（p）和群集的（c）。
vg_extent_count#Ext卷组中的物理扩展数目
vg_extent_sizeExt 卷组中物理扩展的大小
vg_fmtFmt The metadata format of the volume group (lvm2 or lvm1)
vg_freeVFree卷组中剩余可用空间
vg_free_countFree卷组中可用物理扩展数目
vg_nameVG 卷组名称
vg_seqnoSeq 代表修正卷组的数字
vg_sizeVSize卷组大小
vg_sysidSYS IDLVM1 系统 ID
vg_tagsVG Tags附加到卷组中的 LVM 标签
vg_uuidVG UUID卷组的 UUID
vgs 命令默认显示以下字段：vg_name、pv_count、lv_count、snap_count、vg_attr、vg_size、vg_free，并根据 vg_name 排序。 
# vgs
  VG     #PV #LV #SN Attr   VSize  VFree
  new_vg   3   1   1 wz--n- 51.42G 51.36G
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使用带 -v 参数的 vgs 命令向默认显示中添加以下字段：vg_extent_size、vg_uuid。 
# vgs -v
    Finding all volume groups
    Finding volume group "new_vg"
  VG     Attr   Ext   #PV #LV #SN VSize  VFree  VG UUID
  new_vg wz--n- 4.00M   3   1   1 51.42G 51.36G jxQJ0a-ZKk0-OpMO-0118-nlwO-wwqd-fD5D32
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lvs 命令
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表 5.4 “lvs 显示字段” lists the display arguments of the lvs command, along with the field name as it appears in the header display and a description of the field.
Expand
表 5.4. lvs 显示字段
参数标题描述
chunksize
chunk_size
Chunk快照卷的单位大小
copy_percentCopy%镜像卷的同步化比例，还可在使用 pv_move 命令移动物理扩展时使用。
devicesDevices组成逻辑卷的基本设备：物理卷、逻辑卷以及起始物理和逻辑扩展
lv_attrAttr逻辑卷状态。逻辑卷属性字节如下：
Bit 1: Volume type: (m)irrored, (M)irrored without initial sync, (o)rigin, (O)rigin with merging snapshot, (r)aid, (R)aid without initial sync, (s)napshot, merging (S)napshot, (p)vmove, (v)irtual, mirror or raid (i)mage, mirror or raid (I)mage out-of-sync, mirror (l)og device, under (c)onversion, thin (V)olume, (t)hin pool, (T)hin pool data, raid or thin pool m(e)tadata or pool metadata spare,
Bit 2: Permissions: (w)riteable, (r)ead-only, (R)ead-only activation of non-read-only volume
Bit 3: Allocation policy: (a)nywhere, (c)ontiguous, (i)nherited, c(l)ing, (n)ormal. This is capitalized if the volume is currently locked against allocation changes, for example while executing the pvmove command.
字节 4：固定的副号码（m）
Bit 5: State: (a)ctive, (s)uspended, (I)nvalid snapshot, invalid (S)uspended snapshot, snapshot (m)erge failed, suspended snapshot (M)erge failed, mapped (d)evice present without tables, mapped device present with (i)nactive table
字节 6：设备开放（o）
Bit 7: Target type: (m)irror, (r)aid, (s)napshot, (t)hin, (u)nknown, (v)irtual. This groups logical volumes related to the same kernel target together. So, for example, mirror images, mirror logs as well as mirrors themselves appear as (m) if they use the original device-mapper mirror kernel driver, whereas the raid equivalents using the md raid kernel driver all appear as (r). Snapshots using the original device-mapper driver appear as (s), whereas snapshots of thin volumes using the thin provisioning driver appear as (t).
Bit 8: Newly-allocated data blocks are overwritten with blocks of (z)eroes before use.
Bit 9: Volume Health: (p)artial, (r)efresh needed, (m)ismatches exist, (w)ritemostly. (p)artial signifies that one or more of the Physical Volumes this Logical Volume uses is missing from the system. (r)efresh signifies that one or more of the Physical Volumes this RAID Logical Volume uses had suffered a write error. The write error could be due to a temporary failure of that Physical Volume or an indication that it is failing. The device should be refreshed or replaced. (m)ismatches signifies that the RAID logical volume has portions of the array that are not coherent. Inconsistencies are discovered by initiating a check operation on a RAID logical volume. (The scrubbing operations, check and repair, can be performed on a RAID Logical Volume by means of the lvchange command.) (w)ritemostly signifies the devices in a RAID 1 logical volume that have been marked write-mostly.
Bit 10: s(k)ip activation: this volume is flagged to be skipped during activation.
lv_kernel_majorKMaj逻辑卷的真实主设备号码（如果是未激活就减 1）
lv_kernel_minorKMIN逻辑卷的真实副设备号码（如果是未激活就减 1）
lv_majorMaj 逻辑卷持久的主设备号码（如果未指定就减 1）
lv_minorMin 逻辑卷持久的副设备号码（如果未指定就减 1）
lv_nameLV 逻辑卷名称
lv_sizeLSize逻辑卷的大小
lv_tagsLV Tags附加到逻辑卷的 LV 标签
lv_uuidLV UUID逻辑卷的 UUID
mirror_logLog 镜像分支所在设备
modulesModules使用此逻辑卷符合内核设备映射器目标需要
move_pvMove用 pvmove 命令创建的临时逻辑卷的源物理卷
originOrigin快照卷的源设备
regionsize
region_size
Region镜像逻辑卷的单元大小
seg_count#Seg逻辑卷中片段的数目
seg_sizeSSize逻辑卷中片段的大小
seg_startStart修正逻辑卷中的片段
seg_tagsSeg Tags附加到逻辑卷片段的 LVM 标签
segtypeType逻辑卷的片段类型（例如：镜像、条状、线性）
snap_percentSnap%已经使用的快照卷的比例
stripes#Str逻辑卷中条带或者镜像的数目
stripesize
stripe_size
Stripe条状逻辑卷中条带的单位大小
The lvs command displays the following fields by default: lv_name, vg_name, lv_attr, lv_size, origin, snap_percent, move_pv, mirror_log, copy_percent, convert_lv. The default display is sorted by vg_name and lv_name within the volume group. 
# lvs
  LV         VG     Attr   LSize  Origin Snap%  Move Log Copy%  Convert
  lvol0      new_vg owi-a- 52.00M
  newvgsnap1 new_vg swi-a-  8.00M lvol0    0.20
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使用带 -v 参数的 lvs 命令在默认显示结果中添加以下字段：seg_count、lv_major、lv_minor、lv_kernel_major、lv_kernel_minor、lv_uuid。 
# lvs -v
    Finding all logical volumes
  LV         VG     #Seg Attr   LSize  Maj Min KMaj KMin Origin Snap%  Move Copy%  Log Convert LV UUID
  lvol0      new_vg    1 owi-a- 52.00M  -1  -1 253  3                                          LBy1Tz-sr23-OjsI-LT03-nHLC-y8XW-EhCl78
  newvgsnap1 new_vg    1 swi-a-  8.00M  -1  -1 253  5    lvol0    0.20                         1ye1OU-1cIu-o79k-20h2-ZGF0-qCJm-CfbsIx
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您可以使用 lvs 命令的 --segments 参数显示强调片段信息的默认列。当您使用 segments 参数时，seg 前缀是可选的。lvs --segments 命令默认显示以下字段：lv_name、vg_name、lv_attr、stripes、segtype、seg_size。默认显示根据卷组的 vg_name 和 lv_name 排序。如果逻辑卷中有碎片，那么会在此命令的输出结果中显示出来。 
# lvs --segments
  LV       VG         Attr   #Str Type   SSize
  LogVol00 VolGroup00 -wi-ao    1 linear  36.62G
  LogVol01 VolGroup00 -wi-ao    1 linear 512.00M
  lv       vg         -wi-a-    1 linear 104.00M
  lv       vg         -wi-a-    1 linear 104.00M
  lv       vg         -wi-a-    1 linear 104.00M
  lv       vg         -wi-a-    1 linear  88.00M
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使用带 -v 参数的 lvs --segments 命令向默认显示中添加以下字段：seg_start、stripesize、chunksize。 
# lvs -v --segments
    Finding all logical volumes
  LV         VG     Attr   Start SSize  #Str Type   Stripe Chunk
  lvol0      new_vg owi-a-    0  52.00M    1 linear     0     0
  newvgsnap1 new_vg swi-a-    0   8.00M    1 linear     0  8.00K
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下面的例子显示在配置了一个逻辑卷的系统的 lvs 命令的默认输出结果以及指定了 segments 参数的 lvs 命令输出结果。 
# lvs
  LV    VG     Attr   LSize  Origin Snap%  Move Log Copy%
  lvol0 new_vg -wi-a- 52.00M
# lvs --segments
  LV    VG     Attr   #Str Type   SSize
  lvol0 new_vg -wi-a-    1 linear 52.00M
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5.8.3. LVM 报告排序
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通常，lvs、vgs 或者 pvs 命令的完整输出结果在正确排序和对齐之前必须在内部生成并保存。您可以指定 --unbuffered 参数来尽快显示未排序的输出。
要指定另外的列表顺序进行排序，请使用任意报告命令的 -O 参数。在输出中不一定要包含这些输出字段。
下面的例子显示 pvs 命令的输出结果，包括物理卷名称、大小和可用空间。 
# pvs -o pv_name,pv_size,pv_free
  PV         PSize  PFree
  /dev/sdb1  17.14G 17.14G
  /dev/sdc1  17.14G 17.09G
  /dev/sdd1  17.14G 17.14G
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下面的例子显示相同的输出结果，但根据可用空间字段排序。 
# pvs -o pv_name,pv_size,pv_free -O pv_free
  PV         PSize  PFree
  /dev/sdc1  17.14G 17.09G
  /dev/sdd1  17.14G 17.14G
  /dev/sdb1  17.14G 17.14G
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下面的例子表明您不需要根据您要排序的字段显示。 
# pvs -o pv_name,pv_size -O pv_free
  PV         PSize
  /dev/sdc1  17.14G
  /dev/sdd1  17.14G
  /dev/sdb1  17.14G
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要显示逆向排序，请在 -O 参数后您指定的字段前添加 - 符号。 
# pvs -o pv_name,pv_size,pv_free -O -pv_free
  PV         PSize  PFree
  /dev/sdd1  17.14G 17.14G
  /dev/sdb1  17.14G 17.14G
  /dev/sdc1  17.14G 17.09G
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5.8.4. 指定单位
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要指定 LVM 报告显示的单位，请使用报告命令的 --units 参数。您可以指定字节（b）、千字节（k）、兆字节（m）、千兆字节（g）、兆兆字节（t）、艾字节（e）、拍字节（p）以及可读。默认显示是可读。您可以通过在 lvm.conf 文件的 global 部分设定 units 参数来覆盖默认设置。
下面的例子指定 pvs 命令的输出结果以兆为单位，而不是默认的千兆为单位。 
# pvs --units m
  PV         VG     Fmt  Attr PSize     PFree
  /dev/sda1         lvm2 --   17555.40M 17555.40M
  /dev/sdb1  new_vg lvm2 a-   17552.00M 17552.00M
  /dev/sdc1  new_vg lvm2 a-   17552.00M 17500.00M
  /dev/sdd1  new_vg lvm2 a-   17552.00M 17552.00M
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默认情况下，单位显示为 2 的乘方（乘 1024）。您通过大写单位说明（B、K、M、G、T、H）指定将单位显示为乘 1000。
下面的命令以默认行为，即乘 1024 显示输出结果。 
# pvs
  PV         VG     Fmt  Attr PSize  PFree
  /dev/sdb1  new_vg lvm2 a-   17.14G 17.14G
  /dev/sdc1  new_vg lvm2 a-   17.14G 17.09G
  /dev/sdd1  new_vg lvm2 a-   17.14G 17.14G
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下面的命令以乘 1000 显示输出结果。 
#  pvs --units G
  PV         VG     Fmt  Attr PSize  PFree
  /dev/sdb1  new_vg lvm2 a-   18.40G 18.40G
  /dev/sdc1  new_vg lvm2 a-   18.40G 18.35G
  /dev/sdd1  new_vg lvm2 a-   18.40G 18.40G
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您还可以指定扇区（sector，定义为 512K），或者自定义单位。
下面的命令以扇区的数目显示 pvs 命令的输出结果。 
# pvs --units s
  PV         VG     Fmt  Attr PSize     PFree
  /dev/sdb1  new_vg lvm2 a-   35946496S 35946496S
  /dev/sdc1  new_vg lvm2 a-   35946496S 35840000S
  /dev/sdd1  new_vg lvm2 a-   35946496S 35946496S
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The following example displays the output of the pvs command in units of 4 MB. 
# pvs --units 4m
  PV         VG     Fmt  Attr PSize    PFree
  /dev/sdb1  new_vg lvm2 a-   4388.00U 4388.00U
  /dev/sdc1  new_vg lvm2 a-   4388.00U 4375.00U
  /dev/sdd1  new_vg lvm2 a-   4388.00U 4388.00U
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第 6 章 LVM 配置示例
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本章提供了一些基本 LVM 配置示例。

6.1. 在三个磁盘中创建 LVM 逻辑卷
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本示例为创建一个名为 new_logical_volume 的逻辑卷，它由磁盘 /dev/sda1、/dev/sdb1 和 /dev/sdc1 组成。

6.1.1. 创建物理卷
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要在某个卷组中使用磁盘，您需要将它们标记为 LVM 物理卷。

警告

这个命令会破坏 /dev/sda1、/dev/sdb1 和/dev/sdc1 中的所有数据。 
# pvcreate /dev/sda1 /dev/sdb1 /dev/sdc1
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdc1" successfully created
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6.1.2. 创建卷组
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下面的命令可创建卷组 new_vol_group。 
# vgcreate new_vol_group /dev/sda1 /dev/sdb1 /dev/sdc1
  Volume group "new_vol_group" successfully created
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您可以使用 vgs 命令来显示新卷组的属性。 
# vgs
  VG            #PV #LV #SN Attr   VSize  VFree
  new_vol_group   3   0   0 wz--n- 51.45G 51.45G
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6.1.3. 创建逻辑卷
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下面的命令可在卷组 new_vol_group 中创建逻辑卷 new_logical_volume。本示例创建的逻辑卷使用了卷组的 2GB 容量。 
# lvcreate -L2G -n new_logical_volume new_vol_group
  Logical volume "new_logical_volume" created
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6.1.4. 创建文件系统
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The following command creates a GFS2 file system on the logical volume. 
# mkfs.gfs2 -plock_nolock -j 1 /dev/new_vol_group/new_logical_volume
This will destroy any data on /dev/new_vol_group/new_logical_volume.

Are you sure you want to proceed? [y/n] y

Device:                    /dev/new_vol_group/new_logical_volume
Blocksize:                 4096
Filesystem Size:           491460
Journals:                  1
Resource Groups:           8
Locking Protocol:          lock_nolock
Lock Table:

Syncing...
All Done
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下面的命令将逻辑卷挂载到文件系统并报告磁盘空间用量。 
# mount /dev/new_vol_group/new_logical_volume /mnt
[root@tng3-1 ~]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/new_vol_group/new_logical_volume
                       1965840        20   1965820   1% /mnt
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6.2. 创建条状逻辑卷
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本示例为创建一个名为 striped_logical_volume 的条状逻辑卷，并可在磁盘 /dev/sda1、/dev/sdb1 和 /dev/sdc1 间跨磁盘条状分配数据。

6.2.1. 创建物理卷
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将卷组中您要使用的磁盘标记为 LVM 物理卷。

警告

这个命令会破坏 /dev/sda1、/dev/sdb1 和/dev/sdc1 中的所有数据。 
# pvcreate /dev/sda1 /dev/sdb1 /dev/sdc1
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdc1" successfully created
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6.2.2. 创建卷组
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The following command creates the volume group volgroup01. 
# vgcreate volgroup01 /dev/sda1 /dev/sdb1 /dev/sdc1
  Volume group "volgroup01" successfully created
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您可以使用 vgs 命令来显示新卷组的属性。 
# vgs
  VG                #PV #LV #SN Attr   VSize  VFree
  volgroup01          3   0   0 wz--n- 51.45G 51.45G
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6.2.3. 创建逻辑卷
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The following command creates the striped logical volume striped_logical_volume from the volume group volgroup01. This example creates a logical volume that is 2 gigabytes in size, with three stripes and a stripe size of 4 kilobytes. 
# lvcreate -i3 -I4 -L2G -nstriped_logical_volume volgroup01
  Rounding size (512 extents) up to stripe boundary size (513 extents)
  Logical volume "striped_logical_volume" created
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6.2.4. 创建文件系统
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The following command creates a GFS2 file system on the logical volume. 
# mkfs.gfs2 -plock_nolock -j 1 /dev/volgroup01/striped_logical_volume
This will destroy any data on /dev/volgroup01/striped_logical_volume.

Are you sure you want to proceed? [y/n] y

Device:                    /dev/volgroup01/striped_logical_volume
Blocksize:                 4096
Filesystem Size:           492484
Journals:                  1
Resource Groups:           8
Locking Protocol:          lock_nolock
Lock Table:

Syncing...
All Done
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下面的命令将逻辑卷挂载到文件系统并报告磁盘空间用量。 
# mount /dev/volgroup01/striped_logical_volume /mnt
[root@tng3-1 ~]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      13902624   1656776  11528232  13% /
/dev/hda1               101086     10787     85080  12% /boot
tmpfs                   127880         0    127880   0% /dev/shm
/dev/volgroup01/striped_logical_volume
                       1969936        20   1969916   1% /mnt
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6.3. 分割卷组
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在本示例中，现有卷组由三个物理卷组成。如果在物理卷中有足够的未使用空间，就可在不添加新磁盘的情况下创建新的卷组。
在初始设定中，逻辑卷 mylv 是从卷组 myvol 中分割出来的，它依次包含三个物理卷 /dev/sda1、/dev/sdb1 和 /dev/sdc1。
完成这个步骤后，卷组 myvg 将包含 /dev/sda1 和 /dev/sdb1。第二个卷组 yourvg 将包含 /dev/sdc1。

6.3.1. 确定剩余空间
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您可以使用 pvscan 命令来确定在卷组中目前有多少可用的剩余空间。 
# pvscan
  PV /dev/sda1  VG myvg   lvm2 [17.15 GB / 0    free]
  PV /dev/sdb1  VG myvg   lvm2 [17.15 GB / 12.15 GB free]
  PV /dev/sdc1  VG myvg   lvm2 [17.15 GB / 15.80 GB free]
  Total: 3 [51.45 GB] / in use: 3 [51.45 GB] / in no VG: 0 [0   ]
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6.3.2. 转移数据
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您可以使用 pvmove 将 /dev/sdc1 中所有使用的物理扩展移动到 /dev/sdb1 中。执行 pvmove 会花一些时候。 
# pvmove /dev/sdc1 /dev/sdb1
  /dev/sdc1: Moved: 14.7%
  /dev/sdc1: Moved: 30.3%
  /dev/sdc1: Moved: 45.7%
  /dev/sdc1: Moved: 61.0%
  /dev/sdc1: Moved: 76.6%
  /dev/sdc1: Moved: 92.2%
  /dev/sdc1: Moved: 100.0%
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转移完数据后，您可以看到 /dev/sdc1 中的所有空间都可用了。 
# pvscan
  PV /dev/sda1   VG myvg   lvm2 [17.15 GB / 0    free]
  PV /dev/sdb1   VG myvg   lvm2 [17.15 GB / 10.80 GB free]
  PV /dev/sdc1   VG myvg   lvm2 [17.15 GB / 17.15 GB free]
  Total: 3 [51.45 GB] / in use: 3 [51.45 GB] / in no VG: 0 [0   ]
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6.3.3. 分割卷组
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要创建新卷组 yourvg，请使用 vgsplit 命令分割卷组 myvg。
在您可以分割卷组前，必须使逻辑卷失活。如果挂载了文件系统，您必须在失活逻辑卷之前卸载文件系统。
您可以使用 lvchange 命令或者 vgchange 命令使逻辑卷失活。以下命令可以使逻辑卷 mylv 失活并从卷组 myvg 中分割出卷组 yourvg，将物理卷 /dev/sdc1 移动到新的卷组 yourvg 中。 
# lvchange -a n /dev/myvg/mylv
# vgsplit myvg yourvg /dev/sdc1
  Volume group "yourvg" successfully split from "myvg"
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您可以使用 vgs 查看两个卷组的属性。 
# vgs
  VG     #PV #LV #SN Attr   VSize  VFree
  myvg     2   1   0 wz--n- 34.30G 10.80G
  yourvg   1   0   0 wz--n- 17.15G 17.15G
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6.3.4. 创建新逻辑卷
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创建新的卷组后，您可以创建新的逻辑卷 yourlv。 
# lvcreate -L5G -n yourlv yourvg
  Logical volume "yourlv" created
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6.3.5. 生成一个文件系统并挂载到新的逻辑卷
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您可以在新的逻辑卷中生成一个文件系统并挂载它。 
#  mkfs.gfs2 -plock_nolock -j 1 /dev/yourvg/yourlv
This will destroy any data on /dev/yourvg/yourlv.

Are you sure you want to proceed? [y/n] y

Device:                    /dev/yourvg/yourlv
Blocksize:                 4096
Filesystem Size:           1277816
Journals:                  1
Resource Groups:           20
Locking Protocol:          lock_nolock
Lock Table:

Syncing...
All Done

[root@tng3-1 ~]# mount /dev/yourvg/yourlv /mnt
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6.3.6. 激活并挂载原来的逻辑卷
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因为您必须使逻辑卷 mylv 失活，所以您需要在挂载它之前再次激活它。 
# lvchange -a y /dev/myvg/mylv

[root@tng3-1 ~]# mount /dev/myvg/mylv /mnt
[root@tng3-1 ~]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/yourvg/yourlv    24507776        32  24507744   1% /mnt
/dev/myvg/mylv        24507776        32  24507744   1% /mnt
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6.4. 从逻辑卷中删除磁盘
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本示例告诉您如何从现有逻辑卷中删除磁盘，您可以替换磁盘，也可以用这个磁盘作为不同卷的一部分。要删除磁盘，您必须首先将 LVM 物理卷中的扩展移动到不同的磁盘或者一组磁盘中。

6.4.1. 将扩展移动到现有物理卷中
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在本示例中，逻辑卷是在卷组 myvg 中的四个物理卷中进行分配的。 
# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G 15.00G
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我们想要移动 /dev/sdb1 的扩展，以便可以将其从卷组中删除。
如果在卷组的其它物理卷中没有足够的剩余扩展，您可以在您想要删除的设备中执行不带选项的 pvmove 命令，那么扩展就会被分配到其它设备中。 
# pvmove /dev/sdb1
  /dev/sdb1: Moved: 2.0%
 ...
  /dev/sdb1: Moved: 79.2%
 ...
  /dev/sdb1: Moved: 100.0%
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完成 pvmove 命令后，扩展的分配如下： 
# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 17.15G     0
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G 15.00G
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使用 vgreduce 命令从卷组中删除物理卷 /dev/sdb1。 
# vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg"
[root@tng3-1 ~]# pvs
  PV         VG   Fmt  Attr PSize  PFree
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G
  /dev/sdb1       lvm2 --   17.15G 17.15G
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G
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现在可以物理删除这个磁盘或者将其分配给其它用户。

6.4.2. 将扩展移动到新磁盘中
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在本示例中，逻辑卷在卷组 myvg 中按以下方法分配： 
# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdc1  myvg lvm2 a-   17.15G 15.15G  2.00G
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我们想要将 /dev/sdb1> 的扩展移动到新设备 /dev/sdd1 中。
6.4.2.1. 创建新物理卷
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在 /dev/sdd1 中创建新物理卷。 
# pvcreate /dev/sdd1
  Physical volume "/dev/sdd1" successfully created
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6.4.2.2. 将新物理卷添加到卷组中
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将 /dev/sdd1 添加到现有卷组 myvg 中。 
# vgextend myvg /dev/sdd1
  Volume group "myvg" successfully extended
[root@tng3-1]# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1   myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdc1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdd1   myvg lvm2 a-   17.15G 17.15G     0
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6.4.2.3. 转移数据
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使用 pvmove 将数据从 /dev/sdb1 转移到 /dev/sdd1 中。 
# pvmove /dev/sdb1 /dev/sdd1
  /dev/sdb1: Moved: 10.0%
...
  /dev/sdb1: Moved: 79.7%
...
  /dev/sdb1: Moved: 100.0%

[root@tng3-1]# pvs -o+pv_used
  PV          VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1   myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1   myvg lvm2 a-   17.15G 17.15G     0
  /dev/sdc1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdd1   myvg lvm2 a-   17.15G 15.15G  2.00G
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6.4.2.4. 删除卷组中的旧物理卷
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您将数据从 /dev/sdb1 中移走后，您就可以将它从卷组中删除了。 
# vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg"
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现在您可以将这个磁盘重新分配给其它卷组，或者将其从系统中删除。

6.5. Creating a Mirrored LVM Logical Volume in a Cluster
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Creating a mirrored LVM logical volume in a cluster requires the same commands and procedures as creating a mirrored LVM logical volume on a single node. However, in order to create a mirrored LVM volume in a cluster the cluster and cluster mirror infrastructure must be running, the cluster must be quorate, and the locking type in the lvm.conf file must be set correctly to enable cluster locking, either directly or by means of the lvmconf command as described in 第 4.1 节 “在群集中创建 LVM 卷”.
The following procedure creates a mirrored LVM volume in a cluster. First the procedure checks to see whether the cluster services are installed and running, then the procedure creates the mirrored volume.
  1. In order to create a mirrored logical volume that is shared by all of the nodes in a cluster, the locking type must be set correctly in the lvm.conf file in every node of the cluster. By default, the locking type is set to local. To change this, execute the following command in each node of the cluster to enable clustered locking: 
    # /sbin/lvmconf --enable-cluster
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    注意

    As of Red Hat Enterprise Linux 6.7, the lvmconf command provides a --services option that will also enable the services required for LVM in a cluster, a --mirrorservice option that enables the cmirrord service, and a --startstopservices option that immediately starts or stops the services that have been enabled. For information on the lvmconf command, see the lvmconf man page.
  2. To create a clustered logical volume, the cluster infrastructure must be up and running on every node in the cluster. The following example verifies that the clvmd daemon is running on the node from which it was issued: 
     ps auxw | grep clvmd
root     17642  0.0  0.1 32164 1072 ?        Ssl  Apr06   0:00 clvmd -T20 -t 90
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    The following command shows the local view of the cluster status: 
    # cman_tool services
fence domain
member count  3
victim count  0
victim now    0
master nodeid 2
wait state    none
members       1 2 3

dlm lockspaces
name          clvmd
id            0x4104eefa
flags         0x00000000
change        member 3 joined 1 remove 0 failed 0 seq 1,1
members       1 2 3
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  3. Ensure that the cmirror package is installed.
  4. Start the cmirrord service. 
    # service cmirrord start
Starting cmirrord:                                         [  OK  ]
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  5. Create the mirror. The first step is creating the physical volumes. The following commands create three physical volumes. Two of the physical volumes will be used for the legs of the mirror, and the third physical volume will contain the mirror log. 
    # pvcreate /dev/sdb1
  Physical volume "/dev/sdb1" successfully created
[root@doc-07 ~]# pvcreate /dev/sdc1
  Physical volume "/dev/sdc1" successfully created
[root@doc-07 ~]# pvcreate /dev/sdd1
  Physical volume "/dev/sdd1" successfully created
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  6. Create the volume group. This example creates a volume group vg001 that consists of the three physical volumes that were created in the previous step. 
    # vgcreate vg001 /dev/sdb1 /dev/sdc1 /dev/sdd1
  Clustered volume group "vg001" successfully created
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    Note that the output of the vgcreate command indicates that the volume group is clustered. You can verify that a volume group is clustered with the vgs command, which will show the volume group's attributes. If a volume group is clustered, it will show a c attribute. 
     vgs vg001
  VG       #PV #LV #SN Attr   VSize  VFree
  vg001      3   0   0 wz--nc 68.97G 68.97G
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  7. Create the mirrored logical volume. This example creates the logical volume mirrorlv from the volume group vg001. This volume has one mirror leg. This example specifies which extents of the physical volume will be used for the logical volume. 
    # lvcreate -l 1000 -m1 vg001 -n mirrorlv /dev/sdb1:1-1000 /dev/sdc1:1-1000 /dev/sdd1:0
  Logical volume "mirrorlv" created
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    You can use the lvs command to display the progress of the mirror creation. The following example shows that the mirror is 47% synced, then 91% synced, then 100% synced when the mirror is complete. 
    # lvs vg001/mirrorlv
  LV       VG       Attr   LSize Origin Snap%  Move Log           Copy%  Convert
  mirrorlv vg001    mwi-a- 3.91G                    vg001_mlog     47.00
[root@doc-07 log]# lvs vg001/mirrorlv
  LV       VG       Attr   LSize Origin Snap%  Move Log           Copy%  Convert
  mirrorlv vg001    mwi-a- 3.91G                    vg001_mlog     91.00   
[root@doc-07 ~]#  lvs vg001/mirrorlv
  LV       VG       Attr   LSize Origin Snap%  Move Log           Copy%  Convert
  mirrorlv vg001    mwi-a- 3.91G                    vg001_mlog    100.00
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    The completion of the mirror is noted in the system log: 
    May 10 14:52:52 doc-07 [19402]: Monitoring mirror device vg001-mirrorlv for events
May 10 14:55:00 doc-07 lvm[19402]: vg001-mirrorlv is now in-sync
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  8. You can use the lvs with the -o +devices options to display the configuration of the mirror, including which devices make up the mirror legs. You can see that the logical volume in this example is composed of two linear images and one log. 
    # lvs -a -o +devices
  LV                  VG         Attr   LSize  Origin Snap%  Move Log           Copy%  Convert Devices                                  
  mirrorlv            vg001      mwi-a-  3.91G                    mirrorlv_mlog 100.00         mirrorlv_mimage_0(0),mirrorlv_mimage_1(0)
  [mirrorlv_mimage_0] vg001      iwi-ao  3.91G                                                 /dev/sdb1(1)                            
  [mirrorlv_mimage_1] vg001      iwi-ao  3.91G                                                 /dev/sdc1(1)                            
  [mirrorlv_mlog]     vg001      lwi-ao  4.00M                                                 /dev/sdd1(0)
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    You can use the seg_pe_ranges option of the lvs to display the data layout. You can use this option to verify that your layout is properly redundant. The output of this command displays PE ranges in the same format that the lvcreate and lvresize commands take as input. 
    # lvs -a -o +seg_pe_ranges --segments
  PE Ranges                                      
  mirrorlv_mimage_0:0-999 mirrorlv_mimage_1:0-999
  /dev/sdb1:1-1000                              
  /dev/sdc1:1-1000                              
  /dev/sdd1:0-0
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注意

For information on recovering from the failure of one of the legs of an LVM mirrored volume, see 第 7.3 节 “修复 LVM 镜像错误”.

第 7 章 LVM 故障排除
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本章提供了对不同 LVM 问题进行故障排除的操作方法。

7.1. 故障排除诊断
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如果某个命令没有按照预期执行，您可以用以下方法收集诊断信息：
  • 使用命令的 -v、-vv、-vvv 或者 -vvvv 选现提高输出信息的详细程度。
  • If the problem is related to the logical volume activation, set 'activation = 1' in the 'log' section of the configuration file and run the command with the -vvvv argument. After you have finished examining this output be sure to reset this parameter to 0, to avoid possible problems with the machine locking during low memory situations.
  • 运行 lvmdump 命令可为诊断提供信息转储。有关详情请参考 lvmdump(8) man page。
  • 执行 lvs -v、pvs -a 或者 dmsetup info -c 命令以获得额外的系统信息。
  • 检查 /etc/lvm/backup 文件中最后的元数据备份和 /etc/lvm/archive 中的归档版本。
  • Check the current configuration information by running the lvmconfig command.
  • 检查 /etc/lvm 中的 .cache 文件来了解哪些设备中有物理卷。

7.2. 在失败的设备中显示信息。
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You can use the -P argument of the lvs or vgs command to display information about a failed volume that would otherwise not appear in the output. This argument permits some operations even though the metadata is not completely consistent internally. For example, if one of the devices that made up the volume group vg failed, the vgs command might show the following output. 
# vgs -o +devices
  Volume group "vg" not found
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如果您为 vgs 指定了 -P 选项，那么该卷组虽仍然不可用，但您可能看到更多有关失败设备的信息。 
# vgs -P -o +devices
  Partial mode. Incomplete volume groups will be activated read-only.
  VG   #PV #LV #SN Attr   VSize VFree Devices
  vg     9   2   0 rz-pn- 2.11T 2.07T unknown device(0)
  vg     9   2   0 rz-pn- 2.11T 2.07T unknown device(5120),/dev/sda1(0)
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在这个示例中，失败的设备导致卷组中的线性和条状逻辑卷都失败。不带 -P 选项的 lvs 命令会显示以下输出结果。 
# lvs -a -o +devices
  Volume group "vg" not found
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使用 -P 选项显示失败的逻辑卷。 
# lvs -P -a -o +devices
  Partial mode. Incomplete volume groups will be activated read-only.
  LV     VG   Attr   LSize  Origin Snap%  Move Log Copy%  Devices
  linear vg   -wi-a- 20.00G                               unknown device(0)
  stripe vg   -wi-a- 20.00G                               unknown device(5120),/dev/sda1(0)
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下面的例子显示在镜像逻辑卷的一支出错时，带 -P 选项的 pvs 和 lvs 命令的输出结果。 
#  vgs -a -o +devices -P
  Partial mode. Incomplete volume groups will be activated read-only.
  VG    #PV #LV #SN Attr   VSize VFree Devices
  corey   4   4   0 rz-pnc 1.58T 1.34T my_mirror_mimage_0(0),my_mirror_mimage_1(0)
  corey   4   4   0 rz-pnc 1.58T 1.34T /dev/sdd1(0)
  corey   4   4   0 rz-pnc 1.58T 1.34T unknown device(0)
  corey   4   4   0 rz-pnc 1.58T 1.34T /dev/sdb1(0)
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# lvs -a -o +devices -P
  Partial mode. Incomplete volume groups will be activated read-only.
  LV                   VG    Attr   LSize   Origin Snap%  Move Log            Copy%  Devices
  my_mirror            corey mwi-a- 120.00G                    my_mirror_mlog   1.95 my_mirror_mimage_0(0),my_mirror_mimage_1(0)
  [my_mirror_mimage_0] corey iwi-ao 120.00G                                          unknown device(0)
  [my_mirror_mimage_1] corey iwi-ao 120.00G                                          /dev/sdb1(0)
  [my_mirror_mlog]     corey lwi-ao   4.00M                                          /dev/sdd1(0)
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7.3. 修复 LVM 镜像错误
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This section provides an example of recovering from a situation where one leg of an LVM mirrored volume fails because the underlying device for a physical volume goes down and the mirror_log_fault_policy parameter is set to remove, requiring that you manually rebuild the mirror. For information on setting the mirror_log_fault_policy parameter, see 第 5.4.3.1 节 “Mirrored Logical Volume Failure Policy”.
When a mirror leg fails, LVM converts the mirrored volume into a linear volume, which continues to operate as before but without the mirrored redundancy. At that point, you can add a new disk device to the system to use as a replacement physical device and rebuild the mirror.
以下命令创建将用于镜像的物理卷。 
# pvcreate /dev/sd[abcdefgh][12]
  Physical volume "/dev/sda1" successfully created
  Physical volume "/dev/sda2" successfully created
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdb2" successfully created
  Physical volume "/dev/sdc1" successfully created
  Physical volume "/dev/sdc2" successfully created
  Physical volume "/dev/sdd1" successfully created
  Physical volume "/dev/sdd2" successfully created
  Physical volume "/dev/sde1" successfully created
  Physical volume "/dev/sde2" successfully created
  Physical volume "/dev/sdf1" successfully created
  Physical volume "/dev/sdf2" successfully created
  Physical volume "/dev/sdg1" successfully created
  Physical volume "/dev/sdg2" successfully created
  Physical volume "/dev/sdh1" successfully created
  Physical volume "/dev/sdh2" successfully created
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以下命令创建卷组 vg 和镜像卷 groupfs。 
# vgcreate vg /dev/sd[abcdefgh][12]
  Volume group "vg" successfully created
[root@link-08 ~]# lvcreate -L 750M -n groupfs -m 1 vg /dev/sda1 /dev/sdb1 /dev/sdc1
  Rounding up size to full physical extent 752.00 MB
  Logical volume "groupfs" created
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您可以使用 lvs 命令确定镜像卷、用于镜像分支的基本设备以及镜像分支的布局。请注意：在第一个示例中，镜像还没有被完全同步，您应该在 Copy% 字段显示 100.00 之后才继续操作。 
# lvs -a -o +devices
  LV                 VG   Attr   LSize   Origin Snap%  Move Log          Copy% Devices
  groupfs            vg   mwi-a- 752.00M                    groupfs_mlog 21.28 groupfs_mimage_0(0),groupfs_mimage_1(0)
  [groupfs_mimage_0] vg   iwi-ao 752.00M                                       /dev/sda1(0)
  [groupfs_mimage_1] vg   iwi-ao 752.00M                                       /dev/sdb1(0)
  [groupfs_mlog]     vg   lwi-ao   4.00M                                       /dev/sdc1(0)

[root@link-08 ~]# lvs -a -o +devices
  LV                 VG   Attr   LSize   Origin Snap%  Move Log          Copy%  Devices
  groupfs            vg   mwi-a- 752.00M                    groupfs_mlog 100.00 groupfs_mimage_0(0),groupfs_mimage_1(0)
  [groupfs_mimage_0] vg   iwi-ao 752.00M                                        /dev/sda1(0)
  [groupfs_mimage_1] vg   iwi-ao 752.00M                                        /dev/sdb1(0)
  [groupfs_mlog]     vg   lwi-ao   4.00M     i                                  /dev/sdc1(0)
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在这个示例中，镜像 /dev/sda1 的主要分支失败。任何对镜像卷的写入操作都会导致 LVM 去检测失败的镜像。这个时候，LVM 会将镜像转换成单一线性卷。在这里，引起转发的因素是我们执行了 dd 命令。 
# dd if=/dev/zero of=/dev/vg/groupfs count=10
10+0 records in
10+0 records out
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您可以使用 lvs 命令确定该设备现在已经是线性设备了。因为是失败的磁盘，所以会发生 I/O 错误。 
# lvs -a -o +devices
  /dev/sda1: read failed after 0 of 2048 at 0: Input/output error
  /dev/sda2: read failed after 0 of 2048 at 0: Input/output error
  LV      VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  groupfs vg   -wi-a- 752.00M                               /dev/sdb1(0)
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在这里，您应该仍然可以使用逻辑卷，但没有镜像冗余。
To rebuild the mirrored volume, you replace the broken drive and recreate the physical volume. If you use the same disk rather than replacing it with a new one, you will see "inconsistent" warnings when you run the pvcreate command. You can prevent that warning from appearing by executing the vgreduce --removemissing command. 
# pvcreate /dev/sdi[12]
  Physical volume "/dev/sdi1" successfully created
  Physical volume "/dev/sdi2" successfully created

[root@link-08 ~]# pvscan
  PV /dev/sdb1   VG vg   lvm2 [67.83 GB / 67.10 GB free]
  PV /dev/sdb2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdi1           lvm2 [603.94 GB]
  PV /dev/sdi2           lvm2 [603.94 GB]
  Total: 16 [2.11 TB] / in use: 14 [949.65 GB] / in no VG: 2 [1.18 TB]
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下面您可以使用新的物理卷来扩展原来的卷组。 
# vgextend vg /dev/sdi[12]
  Volume group "vg" successfully extended

# pvscan
  PV /dev/sdb1   VG vg   lvm2 [67.83 GB / 67.10 GB free]
  PV /dev/sdb2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdc2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdd2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sde2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdf2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdg2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh1   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdh2   VG vg   lvm2 [67.83 GB / 67.83 GB free]
  PV /dev/sdi1   VG vg   lvm2 [603.93 GB / 603.93 GB free]
  PV /dev/sdi2   VG vg   lvm2 [603.93 GB / 603.93 GB free]
  Total: 16 [2.11 TB] / in use: 16 [2.11 TB] / in no VG: 0 [0   ]
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将线性卷转换回它原来的镜像状态。 
# lvconvert -m 1 /dev/vg/groupfs /dev/sdi1 /dev/sdb1 /dev/sdc1
  Logical volume mirror converted.
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您可以使用 lvs 命令确定恢复到镜像状态。 
# lvs -a -o +devices
  LV                 VG   Attr   LSize   Origin Snap%  Move Log          Copy% Devices
  groupfs            vg   mwi-a- 752.00M                    groupfs_mlog 68.62 groupfs_mimage_0(0),groupfs_mimage_1(0)
  [groupfs_mimage_0] vg   iwi-ao 752.00M                                       /dev/sdb1(0)
  [groupfs_mimage_1] vg   iwi-ao 752.00M                                       /dev/sdi1(0)
  [groupfs_mlog]     vg   lwi-ao   4.00M                                       /dev/sdc1(0)
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7.4. 修复物理卷元数据
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如果不小心覆盖或者破坏了卷组物理卷元数据区域，您会看到出错信息显示元数据区域不正确，或者系统无法使用特定的 UUID 找到物理卷。您可能需要通过在物理卷的元数据区域写入新的元数据来修复物理卷数据，指定相同的 UUID 作为丢失的元数据。

警告

在正常的 LVM 逻辑卷中您应该不会进行这个操作过程。如果您指定了不正确的 UUID，您会丢失您的数据。
下面的例子显示排序的输出解个，您可以看到您的元数据是丢了还是被破坏了。 
# lvs -a -o +devices
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find all physical volumes for volume group VG.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find all physical volumes for volume group VG.
  ...
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通过查看 /etc/lvm/archive 目录，您可能可以找到被覆盖的物理卷 UUID。在文件 VolumeGroupName_xxxx.vg 中查找该卷组最后的有效归档 LVM 元数据。
另外，您可以找到失活的卷并设定 partial （-P）选项，这样您就可以找到丢失的被破坏的物理卷的 UUID。 
# vgchange -an --partial
  Partial mode. Incomplete volume groups will be activated read-only.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  ...
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Use the --uuid and --restorefile arguments of the pvcreate command to restore the physical volume. The following example labels the /dev/sdh1 device as a physical volume with the UUID indicated above, FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk. This command restores the physical volume label with the metadata information contained in VG_00050.vg, the most recent good archived metadata for the volume group. The restorefile argument instructs the pvcreate command to make the new physical volume compatible with the old one on the volume group, ensuring that the new metadata will not be placed where the old physical volume contained data (which could happen, for example, if the original pvcreate command had used the command line arguments that control metadata placement, or if the physical volume was originally created using a different version of the software that used different defaults). The pvcreate command overwrites only the LVM metadata areas and does not affect the existing data areas. 
# pvcreate --uuid "FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk" --restorefile /etc/lvm/archive/VG_00050.vg /dev/sdh1
  Physical volume "/dev/sdh1" successfully created
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You can then use the vgcfgrestore command to restore the volume group's metadata. 
# vgcfgrestore VG
  Restored volume group VG
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现在您可以显示逻辑卷。 
# lvs -a -o +devices
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe VG   -wi--- 300.00G                               /dev/sdh1 (0),/dev/sda1(0)
  stripe VG   -wi--- 300.00G                               /dev/sdh1 (34728),/dev/sdb1(0)
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下面的命令激活卷并显示激活的卷。 
# lvchange -ay /dev/VG/stripe
[root@link-07 backup]# lvs -a -o +devices
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe VG   -wi-a- 300.00G                               /dev/sdh1 (0),/dev/sda1(0)
  stripe VG   -wi-a- 300.00G                               /dev/sdh1 (34728),/dev/sdb1(0)
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如果磁盘中的 LVM 元数据使用至少覆盖了它的数据的空间大小，这个命令可以恢复物理卷。如果覆盖元数据的数据超过了元数据区域，那么就有可能损害到卷中的数据。您可能可以使用 fsck 命令修复那些数据。

7.5. 替换丢失的物理卷
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If a physical volume fails or otherwise needs to be replaced, you can label a new physical volume to replace the one that has been lost in the existing volume group by following the same procedure as you would for recovering physical volume metadata, described in 第 7.4 节 “修复物理卷元数据”. You can use the --partial and --verbose arguments of the vgdisplay command to display the UUIDs and sizes of any physical volumes that are no longer present. If you wish to substitute another physical volume of the same size, you can use the pvcreate command with the --restorefile and --uuid arguments to initialize a new device with the same UUID as the missing physical volume. You can then use the vgcfgrestore command to restore the volume group's metadata.

7.6. 从卷组中删除丢失的物理卷。
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如果您丢失了物理卷，您可以用 vgchange 命令的 --partial 选项激活卷组中剩下的物理卷。您可以使用 vgreduce 命令的 --removemissing 选项删除所有使用卷组中那些物理卷的逻辑卷。
建议您运行 vgreduce 命令，使用 --test 选项来确定您要破坏的数据。
和大多数 LVM 操作一样，vgreduce 命令在某种意义上是可逆的，即您立即使用 vgcfgrestore 命令将卷组的元数据恢复到之前的状态。例如：如果您使用 vgreduce 命令的 --removemissing 参数，而不带 --test 参数，您会找到您要保留的已删除的逻辑卷，您仍可用替换物理卷，并使用另一个 vgcfgrestore 命令来将卷组返回到之前的状态。

7.7. 逻辑卷没有足够的可用扩展
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You may get the error message "Insufficient free extents" when creating a logical volume when you think you have enough extents based on the output of the vgdisplay or vgs commands. This is because these commands round figures to 2 decimal places to provide human-readable output. To specify exact size, use free physical extent count instead of some multiple of bytes to determine the size of the logical volume.
在默认情况下，vgdisplay 命令的输出结果提示可用物理扩展的行。 
# vgdisplay
  --- Volume group ---
  ...
  Free  PE / Size       8780 / 34.30 GB
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另外，您可以使用 vgs 的 vg_free_count 和 vg_extent_count 选项显示可用扩展和扩展的总数。 
# vgs -o +vg_free_count,vg_extent_count
  VG     #PV #LV #SN Attr   VSize  VFree  Free #Ext
  testvg   2   0   0 wz--n- 34.30G 34.30G 8780 8780
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With 8780 free physical extents, you can enter the following command, using the lower-case l argument to use extents instead of bytes: 
# lvcreate -l8780 -n testlv testvg
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这样就会使用卷组中的所有可用扩展。 
# vgs -o +vg_free_count,vg_extent_count
  VG     #PV #LV #SN Attr   VSize  VFree Free #Ext
  testvg   2   1   0 wz--n- 34.30G    0     0 8780
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Alternately, you can extend the logical volume to use a percentage of the remaining free space in the volume group by using the -l argument of the lvcreate command. For information, see 第 5.4.1 节 “Creating Linear Logical Volumes”.

7.8. Duplicate PV Warnings for Multipathed Devices
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When using LVM with multipathed storage, some LVM commands (such as vgs or lvchange) may display messages such as the following when listing a volume group or logical volume. 
Found duplicate PV GDjTZf7Y03GJHjteqOwrye2dcSCjdaUi: using /dev/dm-5 not /dev/sdd
Found duplicate PV GDjTZf7Y03GJHjteqOwrye2dcSCjdaUi: using /dev/emcpowerb not /dev/sde
Found duplicate PV GDjTZf7Y03GJHjteqOwrye2dcSCjdaUi: using /dev/sddlmab not /dev/sdf
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After providing information on the root cause for these warnings, this section describes how to address this issue in the following two cases.
  • The two devices displayed in the output are both single paths to the same device
  • The two devices displayed in the output are both multipath maps

7.8.1. Root Cause of Duplicate PV Warning
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With a default configuration, LVM commands will scan for devices in /dev and check every resulting device for LVM metadata. This is caused by the default filter in the /etc/lvm/lvm.conf, which is as follows: 
filter = [ "a/.*/" ]
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When using Device Mapper Multipath or other multipath software such as EMC PowerPath or Hitachi Dynamic Link Manager (HDLM), each path to a particular logical unit number (LUN) is registered as a different SCSI device, such as /dev/sdb or /dev/sdc. The multipath software will then create a new device that maps to those individual paths, such as /dev/mapper/mpath1 or /dev/mapper/mpatha for Device Mapper Multipath, /dev/emcpowera for EMC PowerPath, or /dev/sddlmab for Hitachi HDLM. Since each LUN has multiple device nodes in /dev that point to the same underlying data, they all contain the same LVM metadata and thus LVM commands will find the same metadata multiple times and report them as duplicates.
These duplicate messages are only warnings and do not mean the LVM operation has failed. Rather, they are alerting the user that only one of the devices has been used as a physical volume and the others are being ignored. If the messages indicate the incorrect device is being chosen or if the warnings are disruptive to users, then a filter can be applied to search only the necessary devices for physical volumes, and to leave out any underlying paths to multipath devices.

7.8.2. Duplicate Warnings for Single Paths
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The following example shows a duplicate PV warning in which the duplicate devices displayed are both single paths to the same device. In this case, both /dev/sdd and /dev/sdf can be found under the same multipath map in the output to the multipath -ll command. 
Found duplicate PV GDjTZf7Y03GJHjteqOwrye2dcSCjdaUi: using **/dev/sdd** not **/dev/sdf**
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To prevent this warning from appearing, you can configure a filter in the /etc/lvm/lvm.conf file to restrict the devices that LVM will search for metadata. The filter is a list of patterns that will be applied to each device found by a scan of /dev (or the directory specified by the dir keyword in the /etc/lvm/lvm.conf file). Patterns are regular expressions delimited by any character and preceded by a (for accept) or r (for reject). The list is traversed in order, and the first regex that matches a device determines if the device will be accepted or rejected (ignored). Devices that don’t match any patterns are accepted. For general information on LVM filters, see 第 5.5 节 “用过滤器控制 LVM 设备扫描”.
The filter you configure should include all devices that need to be checked for LVM metadata, such as the local hard drive with the root volume group on it and any multipathed devices. By rejecting the underlying paths to a multipath device (such as /dev/sdb, /dev/sdd, and so on) you can avoid these duplicate PV warnings, since each unique metadata area will only be found once on the multipath device itself.
The following examples show filters that will avoid duplicate PV warnings due to multiple storage paths being available.
  • This filter accepts the second partition on the first hard drive (/dev/sda and any device-mapper-multipath devices, while rejecting everything else. 
    filter = [ "a|/dev/sda2$|", "a|/dev/mapper/mpath.*|", "r|.*|" ]
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  • This filter accepts all HP SmartArray controllers and any EMC PowerPath devices. 
    filter = [ "a|/dev/cciss/.*|", "a|/dev/emcpower.*|", "r|.*|" ]
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  • This filter accepts any partitions on the first IDE drive and any multipath devices. 
    filter = [ "a|/dev/hda.*|", "a|/dev/mapper/mpath.*|", "r|.*|" ]
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注意

When adding a new filter to the /etc/lvm/lvm.conf file, ensure that the original filter is either commented out with a # or is removed.
Once a filter has been configured and the /etc/lvm/lvm.conf file has been saved, check the output of these commands to ensure that no physical volumes or volume groups are missing. 
# pvscan
# vgscan
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You can also test a filter on the fly, without modifying the /etc/lvm/lvm.conf file, by adding the --config argument to the LVM command, as in the following example. 
# lvs --config 'devices{ filter = [ "a|/dev/emcpower.*|", "r|.*|" ] }'
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注意

Testing filters using the --config argument will not make permanent changes to the server's configuration. Make sure to include the working filter in the /etc/lvm/lvm.conf file after testing.
After configuring an LVM filter, it is recommended that you rebuild the initrd device with the dracut command so that only the necessary devices are scanned upon reboot.

7.8.3. Duplicate Warnings for Multipath Maps
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The following examples show a duplicate PV warning for two devices that are both multipath maps. In these examples we are not looking at two different paths, but two different devices. 
Found duplicate PV GDjTZf7Y03GJHjteqOwrye2dcSCjdaUi: using **/dev/mapper/mpatha** not **/dev/mapper/mpathc**
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Found duplicate PV GDjTZf7Y03GJHjteqOwrye2dcSCjdaUi: using **/dev/emcpowera** not **/dev/emcpowerh**
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This situation is more serious than duplicate warnings for devices that are both single paths to the same device, since these warnings often mean that the machine has been presented devices which it should not be seeing (for example, LUN clones or mirrors). In this case, unless you have a clear idea of what devices should be removed from the machine, the situation could be unrecoverable. It is recommended that you contact Red Hat Technical Support to address this issue.

第 8 章 用 LVM GUI 进行 LVM 管理
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In addition to the Command Line Interface (CLI), LVM provides a Graphical User Interface (GUI) which you can use to configure LVM logical volumes. You can open this utility by typing system-config-lvm. The LVM chapter of the Storage Administration Guide provides step-by-step instructions for configuring an LVM logical volume using this utility.

附录 A. 设备映射器（Device Mapper）
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设备映射器是一个为卷管理提供通用构架的内核驱动程序。它提供可用来创建用作逻辑卷设备的映射设备的通用方法。它不一定要特别了解卷组或者元数据格式。
设备映射器为一组高级技术提供了基础。除 LVM 之外，设备映射器多路径和 dmraid 命令也使用设备映射器。设备映射器的应用程序界面是ioctl 系统调用。用户界面是 dmsetup 命令。
LVM logical volumes are activated using the Device Mapper. Each logical volume is translated into a mapped device. Each segment translates into a line in the mapping table that describes the device. The Device Mapper supports a variety of mapping targets, including linear mapping, striped mapping, and error mapping. So, for example, two disks may be concatenated into one logical volume with a pair of linear mappings, one for each disk. When LVM creates a volume, it creates an underlying device-mapper device that can be queried with the dmsetup command. For information about the format of devices in a mapping table, see 第 A.1 节 “设备列表映射”. For information about using the dmsetup command to query a device, see 第 A.2 节 “dmsetup 命令”.

A.1. 设备列表映射
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映射的设备是由一个列表定义的，该列表指定如何使用支持的设备列表映射将设备的每个逻辑分段行进行匹配。映射设备的列表由以下格式行组成： 
start length mapping [mapping_parameters...]
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在设备映射列表的第一行中，start 参数必须等于 0。某行中的 start + length 参数必须与下一行的 start 相等。在映射列表中指定哪个映射参数取决于在该行中指定的 mapping 类型。
设备映射器中的大小总是以扇区（512 字节）为单位指定。
当将某个设备指定为设备映射器中的映射参数，它就被该文件系统（比如 /dev/hda）中的设备名称或者主号码和副号码以 major:minor 的格式进行参考。首选 major:minor 格式因为这样可避免查找路径名称。
以下显示了某设备的映像列表示例。在这个列表中有四个线性对象： 
0 35258368 linear 8:48 65920
35258368 35258368 linear 8:32 65920
70516736 17694720 linear 8:16 17694976
88211456 17694720 linear 8:16 256
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每行的前两个参数是片段起始块以及该片段的长度。下一个关键字是映射对象，在此示例中全部是 linear。该行的其余部分包括用于线性对象的参数。
The following subsections describe these mapping formats:
  • 线性
  • 条状
  • 镜像
  • 快照以及 snapshot-origin
  • 错误
  • 零
  • 多路径
  • 加密
  • device-mapper RAID
  • thin
  • thin-pool

A.1.1. 线性映射对象
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线性映射对象将块的连续行映射到另一个块设备中。线性对象的格式如下： 
start length linear device offset
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start
虚拟设备中的起始块
length
这个片段的长度
device
块设备，被该文件系统中的设备名称或者主号码和副号码以 major:minor 的格式参考
offset
该设备中映射的起始误差
以下示例显示了起始块位于虚拟设备 0，片段长度为 1638400，major:minor 号码对为 8:2，起始误差为 41146992 的线性对象。 
0 16384000 linear 8:2 41156992
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以下示例是含有在设备 /dev/hda 中指定的设备参数的线性对象。 
0 20971520 linear /dev/hda 384
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A.1.2. 条状映射对象
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条状映射对象支持所有跨物理设备的条块。它使用条块数目和成条的组集大小以及设备名称和扇区对作为参数。条状对象的格式如下： 
start length striped #stripes chunk_size device1 offset1 ... deviceN offsetN
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每个条块都有一组 device 和 offset 参数。
start
虚拟设备中的起始块
length
这个片段的长度
#stripes
虚拟设备的条数
chunk_size
切换到下一个条之前写入每个条的扇区数，必须至少是内核页面大小的两倍
device
块设备，可被该文件系统中的设备名称或者主号码和副号码以格式 major:minor 参考。
offset
该设备中映射的起始误差
以下示例显示了一个有三个条，且组集大小为 128 的条状对象： 
0 73728 striped 3 128 8:9 384 8:8 384 8:7 9789824
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0
虚拟设备中的起始块
73728
这个片段的长度
striped 3 128
三个设备中组集大小为 128 块的条
8:9
第一个设备的 major:minor 号码
384
第一个设备中映射的起始误差
8:8
第二个设备的 major:minor 号码
384
第二个设备中映射的起始误差
8:7
major:minor numbers of third device
9789824
第三个设备中映射的起始误差
以下示例显示了含有两个 256KiB 条，使用文件系统中的设备名称而不是主号码和副号码指定设备参数的条状对象。 
0 65536 striped 2 512 /dev/hda 0 /dev/hdb 0
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A.1.3. 镜像映射对象
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镜像映射对象支持镜像的逻辑设备。镜像对象格式如下： 
start length mirror log_type #logargs logarg1 ... logargN #devs device1 offset1 ... deviceN offsetN
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start
虚拟设备中的起始块
length
这个片段的长度
log_type
可能的日志类型及其参数如下：
core
镜像是本地的，镜像日志保存在核内存中。这个日志类型有 1-3 个参数：
regionsize [[no]sync] [block_on_error]
disk
镜像是本地的，镜像日志保存在磁盘中。这个日志类型有 2-4 个参数：
logdevice regionsize [[no]sync] [block_on_error]
clustered_core
镜像是群集的，镜像日志保存在核内存中。这个日志类型有 2-4 个参数：
regionsize UUID [[no]sync] [block_on_error]
clustered_disk
镜像是群集的，镜像日志保存在磁盘中。这个日志类型有 3-5 个参数：
logdevice regionsize UUID [[no]sync] [block_on_error]
LVM 保存一个小日志用来跟踪与该镜像或者多个镜像同步的区域。regionsize 参数指定这些区域的大小。
在群集环境中，UUID 参数是与镜像日志设备关联的特定识别符，以便可通过该群集维护日志状态。
The optional [no]sync argument can be used to specify the mirror as "in-sync" or "out-of-sync". The block_on_error argument is used to tell the mirror to respond to errors rather than ignoring them.
#log_args
将在映射中指定的日志参数数目
logargs
镜像的日志参数；提供的日志参数数目是由 #log-args 参数指定的，且有效日志参数由 log_type 参数决定。
#devs
the number of legs in the mirror; a device and an offset is specified for each leg
device
每个镜像分支的块设备，使用该文件系统中的设备名称或者主号码和副号码以 major:minor 的格式参考。每个镜像分支都有一个块设备和误差，如 #devs 参数中所示。
offset
设备中映射的起始误差。每个镜像分支都有一个块设备和误差，如 #devs 参数中所示。
以下示例显示了某个镜像日志保存在磁盘中的群集镜像的镜像映射对象。 
0 52428800 mirror clustered_disk 4 253:2 1024 UUID block_on_error 3 253:3 0 253:4 0 253:5 0
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0
虚拟设备中的起始块
52428800
这个片段的长度
mirror clustered_disk
日志类型指定其为群集镜像且镜像日志保存在磁盘中的镜像对象
4
附带 4 个镜像日志参数
253:2
日志设备的 major:minor 号码
1024
镜像日志用来跟踪哪些进行同步的区域大小
UUID
镜像日志的 UUID，用来通过群集维护日志信息
block_on_error
镜像应该响应错误
3
镜像中的分支
253:3 0 253:4 0 253:5 0
构成镜像的每个分支的设备的 major:minor 号码和误差

A.1.4. 快照以及 snapshot-origin 映射对象
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当您生成某个卷的第一个 LVM 快照时，要使用四个设备映射器设备：
  1. 包含源卷原始映射列表线性映射的设备。
  2. 作为源卷即写即拷（copy-on-write，COW）设备使用的有线性映射的设备；每次写入时，会将原始数据保存在每个快照的 COW 设备中以便保持不更改可见内容（直到 COW 设备写满为止）。
  3. A device with a snapshot mapping combining #1 and #2, which is the visible snapshot volume.
  4. The "original" volume (which uses the device number used by the original source volume), whose table is replaced by a "snapshot-origin" mapping from device #1.
用来创建这些设备的固定命名方案，例如：您可以使用以下命令生成名为 base 的 LVM 卷以及基于该卷的名为 snap 快照卷。 
# lvcreate -L 1G -n base volumeGroup
# lvcreate -L 100M --snapshot -n snap volumeGroup/base
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这产生四个设备，您可以使用以下命令浏览： 
# dmsetup table|grep volumeGroup
volumeGroup-base-real: 0 2097152 linear 8:19 384
volumeGroup-snap-cow: 0 204800 linear 8:19 2097536
volumeGroup-snap: 0 2097152 snapshot 254:11 254:12 P 16
volumeGroup-base: 0 2097152 snapshot-origin 254:11

# ls -lL /dev/mapper/volumeGroup-*
brw-------  1 root root 254, 11 29 ago 18:15 /dev/mapper/volumeGroup-base-real
brw-------  1 root root 254, 12 29 ago 18:15 /dev/mapper/volumeGroup-snap-cow
brw-------  1 root root 254, 13 29 ago 18:15 /dev/mapper/volumeGroup-snap
brw-------  1 root root 254, 10 29 ago 18:14 /dev/mapper/volumeGroup-base
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snapshot-origin 对象的格式如下： 
start length snapshot-origin origin
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start
虚拟设备中的起始块
length
这个片段的长度
origin
快照基础卷
snapshot-origin 一般有一个或者多个基于它的快照。会将读取操作直接与后备设备映射。每次写入时，会将原始数据保存在每个快照的 COW 设备中以便保持其不更改的可见内容（直到 COW 设备写满为止）。
快照对象的格式如下： 
start length snapshot origin COW-device P|N chunksize
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start
虚拟设备中的起始块
length
这个片段的长度
origin
快照基础卷
COW-device
保存更改组集的设备
P|N
P（持久）或者N（不持久）；指示快照是否可在重启后保留。对于瞬时快照（N）必须将 less metadata 保存在磁盘中；内核可将其保存在内存中。
chunksize
将保存到 COW 设备中的有数据更改的组集的扇区的大小
以下示例显示了起始设备为 254:11 的 snapshot-origin 对象。 
0 2097152 snapshot-origin 254:11
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以下示例显示了起始设备为 254:11、COW 设备为 254:12 的 snapshot-origin 对象。这个快照设备在重启后仍然保留，且保存在 COW 设备中的数据组集大小为 16 个扇区。 
0 2097152 snapshot 254:11 254:12 P 16
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A.1.5. 错误映射对象
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如果有错误映射对象，任何对映射的扇区的 I/O 操作会失败。
错误映射可用来进行测试。要测试某个设备在失败后如何动作，您可以创建一个设备映射，且在该设备中部有一个坏扇区，或者您可以换出一个镜像分支并用错误对象替换之。
An error target can be used in place of a failing device, as a way of avoiding timeouts and retries on the actual device. It can serve as an intermediate target while you rearrange LVM metadata during failures.
错误映射对象除 start 和 length 参数外不使用其它参数。
以下示例显示的是错误对象。 
0 65536 error
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A.1.6. 零映射对象
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零映射对象是与 /dev/zero 等同的块设备。对这个映射的读取操作会返回零块。写入这个映射的数据会被丢弃，但写入操作会成功。零映射对象除 start 和 length 参数外没有其它参数。
以下示例显示了一个 16Tb 设备的零对象。 
0 65536 zero
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A.1.7. 多路径映射对象
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多路径映射对象支持多路径的设备的映射。多路径对象的格式如下： 
start length  multipath  #features [feature1 ... featureN] #handlerargs [handlerarg1 ... handlerargN] #pathgroups pathgroup pathgroupargs1 ... pathgroupargsN
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每个路径组群都有一组 pathgroupargs 参数。
start
虚拟设备中的起始块
length
这个片段的长度
#features
The number of multipath features, followed by those features. If this parameter is zero, then there is no feature parameter and the next device mapping parameter is #handlerargs. Currently there is one supported feature that can be set with the features attribute in the multipath.conf file, queue_if_no_path. This indicates that this multipathed device is currently set to queue I/O operations if there is no path available.
In the following example, the no_path_retry attribute in the multipath.conf file has been set to queue I/O operations only until all paths have been marked as failed after a set number of attempts have been made to use the paths. In this case, the mapping appears as follows until all the path checkers have failed the specified number of checks. 
0 71014400 multipath 1 queue_if_no_path 0 2 1 round-robin 0 2 1 66:128 \
1000 65:64 1000 round-robin 0 2 1 8:0 1000 67:192 1000
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在所有路径检查程序完成指定数目的检查并失败后，会出现如下映射。 
0 71014400 multipath 0 0 2 1 round-robin 0 2 1 66:128 1000 65:64 1000 \
round-robin 0 2 1 8:0 1000 67:192 1000
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#handlerargs
那些参数后是硬件处理器参数的数目。硬件处理器指定在切换路径组或者处理 I/O 错误时用来执行硬件特定的动作。如果将其设定为 0，那么下一个参数则为 #pathgroups。
#pathgroups
路径组的数目。一个路径组是一组多路径的设备进行负载平衡的路径。每个路径组都有一组 pathgroupargs 参数。
pathgroup
下一个要尝试的路径组。
pathgroupsargs
每个路径组包括以下参数： 
pathselector #selectorargs #paths #pathargs device1 ioreqs1 ... deviceN ioreqsN
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路径组中的每个路径都有一组路径参数。
pathselector
指定用来决定使用这个路径组中的哪个路径进行下一个 I/O 操作的算法。
#selectorargs
在多路径映射中这个参数后的路径选择程序参数的数目。目前，这个参数的值总是 0。
#paths
这个路径组中的路径数目。
#pathargs
在这个组群中为每个路径指定的路径参数数目。目前，这个数值总是 1，即 ioreqs 参数。
device
该路径的块设备，使用主号码和副号码以 major:minor 格式参考
ioreqs
切换到当前组群的下一个路径前路由到这个路径的 I/O 请求数目。
图 A.1 “多路径映射对象” shows the format of a multipath target with two path groups.
多路径映射对象
View larger image
多路径映射对象

图 A.1. 多路径映射对象

以下示例显示对同一个多路径设备的一个纯故障排除对象定义。在这个对象中有四个路径组，其中每个路径组只有一个路径，以便多路径的设备每次只能使用一个路径。 
0 71014400 multipath 0 0 4 1 round-robin 0 1 1 66:112 1000 \
round-robin 0 1 1 67:176 1000 round-robin 0 1 1 68:240 1000 \
round-robin 0 1 1 65:48 1000
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以下示例显示为同一个多路径设备完全展开（多总线）对象定义。在这个对象中只有一个路径组，其中包含所有路径。在这个设定中，多路径将所有负载平均分配到所有路径中。 
0 71014400 multipath 0 0 1 1 round-robin 0 4 1 66:112 1000 \
 67:176 1000 68:240 1000 65:48 1000
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有关多路径的详情请参考《使用设备映射器多路径》文档。

A.1.8. 加密映射对象
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加密对象会加密通过指定设备的所有数据。它使用内核 Crypto API。
加密对象的格式如下： 
start length crypt cipher key IV-offset device offset
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start
虚拟设备中的起始块
length
这个片段的长度
cipher
Cipher 包含 cipher[-chainmode]-ivmode[:iv options]。
cipher
可用密码位于 /proc/crypto（例如：aes）。
chainmode
总是使用 cbc。不要使用 ebc，它不使用初始向量（IV）。
ivmode[:iv options]
IV is an initial vector used to vary the encryption. The IV mode is plain or essiv:hash. An ivmode of -plain uses the sector number (plus IV offset) as the IV. An ivmode of -essiv is an enhancement avoiding a watermark weakness.
key
加密密钥，在 hex 中提供
IV-offset
初始向量（IV）误差
device
块设备，被该文件系统中的设备名称或者主号码和副号码以 major:minor 的格式参考
offset
该设备中映射的起始误差
以下是加密对象示例。 
0 2097152 crypt aes-plain 0123456789abcdef0123456789abcdef 0 /dev/hda 0
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A.1.9. The device-mapper RAID Mapping Target
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The device-mapper RAID (dm-raid) target provides a bridge from DM to MD. It allows the MD RAID drivers to be accessed using a device-mapper interface. The format of the dm-raid target is as follows 
start length raid raid_type #raid_params raid_params #raid_devs metadata_dev0 dev0 [.. metadata_devN devN]
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start
虚拟设备中的起始块
length
这个片段的长度
raid_type
The RAID type can be one of the following
raid1
RAID1 mirroring
raid4
RAID4 dedicated parity disk
raid5_la
RAID5 left asymmetric
— rotating parity 0 with data continuation
raid5_ra
RAID5 right asymmetric
— rotating parity N with data continuation
raid5_ls
RAID5 left symmetric
— rotating parity 0 with data restart
raid5_rs
RAID5 right symmetric
— rotating parity N with data restart
raid6_zr
RAID6 zero restart
— rotating parity 0 (left to right) with data restart
raid6_nr
RAID6 N restart
— rotating parity N (right to left) with data restart
raid6_nc
RAID6 N continue
— rotating parity N (right to left) with data continuation
raid10
Various RAID10-inspired algorithms selected by further optional arguments
— RAID 10: Striped mirrors (striping on top of mirrors)
— RAID 1E: Integrated adjacent striped mirroring
— RAID 1E: Integrated offset striped mirroring
— Other similar RAID10 variants
#raid_params
The number of parameters that follow
raid_params
Mandatory parameters:
chunk_size
Chunk size in sectors. This parameter is often known as "stripe size". It is the only mandatory parameter and is placed first.
Followed by optional parameters (in any order):
[sync|nosync]
Force or prevent RAID initialization.
rebuild idx
Rebuild drive number idx (first drive is 0).
daemon_sleep ms
Interval between runs of the bitmap daemon that clear bits. A longer interval means less bitmap I/O but resyncing after a failure is likely to take longer.
min_recovery_rate KB/sec/disk
Throttle RAID initialization
max_recovery_rate KB/sec/disk
Throttle RAID initialization
write_mostly idx
Mark drive index idx write-mostly.
max_write_behind sectors
See the description of --write-behind in the mdadm man page.
stripe_cache sectors
Stripe cache size (RAID 4/5/6 only)
region_size sectors
The region_size multiplied by the number of regions is the logical size of the array. The bitmap records the device synchronization state for each region.
raid10_copies #copies
The number of RAID10 copies. This parameter is used in conjunction with the raid10_format parameter to alter the default layout of a RAID10 configuration. The default value is 2.
raid10_format near|far|offset
This parameter is used in conjunction with the raid10_copies parameter to alter the default layout of a RAID10 configuration. The default value is near, which specifies a standard mirroring layout.
If the raid10_copies and raid10_format are left unspecified, or raid10_copies 2 and/or raid10_format near is specified, then the layouts for 2, 3 and 4 devices are as follows: 
2 drives    3 drives      4 drives
--------    ----------    --------------
A1  A1      A1  A1  A2    A1  A1  A2  A2
A2  A2      A2  A3  A3    A3  A3  A4  A4
A3  A3      A4  A4  A5    A5  A5  A6  A6
A4  A4      A5  A6  A6    A7  A7  A8  A8
..  ..      ..  ..  ..    ..  ..  ..  ..
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The 2-device layout is equivalent to 2-way RAID1. The 4-device layout is what a traditional RAID10 would look like. The 3-device layout is what might be called a 'RAID1E - Integrated Adjacent Stripe Mirroring'.
If raid10_copies 2 and raid10_format far are specified, then the layouts for 2, 3 and 4 devices are as follows: 
2 drives    3 drives        4 drives
--------   -----------      ------------------
A1  A2      A1  A2  A3      A1   A2   A3   A4
A3  A4      A4  A5  A6      A5   A6   A7   A8
A5  A6      A7  A8  A9      A9   A10  A11  A12
..  ..      ..  ..  ..      ..   ..   ..   ..
A2  A1      A3  A1  A2      A2   A1   A4   A3
A4  A3      A6  A4  A5      A6   A5   A8   A7
A6  A5      A9  A7  A8      A10  A9   A12  A11
..  ..      ..  ..  ..      ..   ..   ..   ..
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If raid10_copies 2 and raid10_format offset are specified, then the layouts for 2, 3 and 4 devices are as follows: 
2 drives    3 drives       4 drives
--------    --------       ------------------
A1  A2      A1  A2  A3     A1   A2   A3   A4
A2  A1      A3  A1  A2     A2   A1   A4   A3
A3  A4      A4  A5  A6     A5   A6   A7   A8
A4  A3      A6  A4  A5     A6   A5   A8   A7
A5  A6      A7  A8  A9     A9   A10  A11  A12
A6  A5      A9  A7  A8     A10  A9   A12  A11
..  ..      ..  ..  ..     ..   ..   ..   ..
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These layouts closely resemble the layouts fo RAID1E - Integrated Offset Stripe Mirroring'
#raid_devs
The number of devices composing the array
Each device consists of two entries. The first is the device containing the metadata (if any); the second is the one containing the data.
If a drive has failed or is missing at creation time, a '-' can be given for both the metadata and data drives for a given position.
The following example shows a RAID4 target with a starting block of 0 and a segment length of 1960893648. There are 4 data drives, 1 parity, with no metadata devices specified to hold superblock/bitmap info and a chunk size of 1MiB 
0 1960893648 raid raid4 1 2048 5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81
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The following example shows a RAID4 target with a starting block of 0 and a segment length of 1960893648. there are 4 data drives, 1 parity, with metadata devices, a chunk size of 1MiB, force RAID initialization, and a min_recovery rate of 20 kiB/sec/disks. 
0 1960893648 raid raid4 4 2048 sync min_recovery_rate 20 5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 8:66 8:81 8:82
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A.1.10. The thin and thin-pool Mapping Targets
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The format of a thin-pool target is as follows: 
start length thin-pool metadata_dev data_dev data_block_size low_water_mark [#feature_args [arg*] ]
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start
虚拟设备中的起始块
length
这个片段的长度
metadata_dev
The metadata device
data_dev
The data device
data_block_size
The data block size (in sectors). The data block size gives the smallest unit of disk space that can be allocated at a time expressed in units of 512-byte sectors. Data block size must be between 64KB (128 sectors) and 1GB (2097152 sectors) inclusive and it must be a mutlipole of 128 (64KB).
low_water_mark
The low water mark, expressed in blocks of size data_block_size. If free space on the data device drops below this level then a device-mapper event will be triggered which a user-space daemon should catch allowing it to extend the pool device. Only one such event will be sent. Resuming a device with a new table itself triggers an event so the user-space daemon can use this to detect a situation where a new table already exceeds the threshold.
A low water mark for the metadata device is maintained in the kernel and will trigger a device-mapper event if free space on the metadata device drops below it.
#feature_args
The number of feature arguments
arg
The thin pool feature argument are as follows:
skip_block_zeroing
Skip the zeroing of newly-provisioned blocks.
ignore_discard
Disable discard support.
no_discard_passdown
Do not pass discards down to the underlying data device, but just remove the mapping.
read_only
Do not allow any changes to be made to the pool metadata.
error_if_no_space
Error IOs, instead of queuing, if no space.
The following example shows a thin-pool target with a starting block in the virtual device of 0, a segment length of 1638400. /dev/sdc1 is a small metadata device and /dev/sdc2 is a larger data device. The chunksize is 64k, the low_water_mark is 0, and there are no features. 
0 16384000 thin-pool /dev/sdc1 /dev/sdc2 128 0 0
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The format of a thin target is as follows: 
start length thin pool_dev dev_id [external_origin_dev]
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start
虚拟设备中的起始块
length
这个片段的长度
pool_dev
The thin-pool device, for example /dev/mapper/my_pool or 253:0
dev_id
The internal device identifier of the device to be activated.
external_origin_dev
An optional block device outside the pool to be treated as a read-only snapshot origin. Reads to unprovisioned areas of the thin target will be mapped to this device.
The following example shows a 1 GiB thinLV that uses /dev/mapper/pool as its backing store (thin-pool). The target has a starting block in the virtual device of 0 and a segment length of 2097152. 
0 2097152 thin /dev/mapper/pool 1
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A.2. dmsetup 命令
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dmsetup 命令是一个用来与设备映射器沟通的命令行封装器（wrapper）。对于 LVM 设备的一般系统信息，您可发现 dmsetup 命令的 info、ls、status 和 deps 选项是有用的，如以下部分所述。
有关 dmsetup 命令的额外选项和功能，请参考 dmsetup(8) man page。

A.2.1. dmsetup info 命令
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dmsetup info device 命令提供有关设备映射器设备概述。如果您没有指定设备名称，则输出所余目前配置的设备映射器设备信息。如果您指定了一个设备，那么这个命令只会生成那个设备的信息。
dmsetup info 命令提供以下分类中的信息：
Name
The name of the device. An LVM device is expressed as the volume group name and the logical volume name separated by a hyphen. A hyphen in the original name is translated to two hyphens. During standard LVM operations, you should not use the name of an LVM device in this format to specify an LVM device directly, but instead you should use the vg/lv alternative.
State
可能的设备状态是 SUSPENDED、ACTIVE 和 READ-ONLY。dmsetup suspend 命令将设备状态设定为 SUSPENDED。当挂起某个设备时，所有到那个设备的 I/O 操作都会停止。dmsetup resume 命令将设备状态恢复到 ACTIVE。
Read Ahead
系统对任意正在进行读取操作的打开的文件提前读取的数据块的数目。模热情况下，内核会自动选择一个合适的值。您可使用 dmsetup 命令的 --readahead 选项更改这个值。
Tables present
Possible states for this category are LIVE and INACTIVE. An INACTIVE state indicates that a table has been loaded which will be swapped in when a dmsetup resume command restores a device state to ACTIVE, at which point the table's state becomes LIVE. For information, see the dmsetup man page.
Open count
打开参考计数指示该打开该设备的次数。mount 命令会打开一个设备。
Event number
The current number of events received. Issuing a dmsetup wait n command allows the user to wait for the n'th event, blocking the call until it is received.
Major, minor
主设备号码和副设备号码
Number of targets
组成一个设备的片段数目。例如：一个跨越三个磁盘的线性设备会有三个对象。由一个磁盘起始和结尾，而不是中间组成的线性设备有两个设备。
UUID
该设备的 UUID。
以下是 dmsetup info 命令的部分输出示例。 
# dmsetup info
Name:              testgfsvg-testgfslv1
State:             ACTIVE
Read Ahead:        256
Tables present:    LIVE
Open count:        0
Event number:      0
Major, minor:      253, 2
Number of targets: 2
UUID: LVM-K528WUGQgPadNXYcFrrf9LnPlUMswgkCkpgPIgYzSvigM7SfeWCypddNSWtNzc2N
...
Name:              VolGroup00-LogVol00
State:             ACTIVE
Read Ahead:        256
Tables present:    LIVE
Open count:        1
Event number:      0
Major, minor:      253, 0
Number of targets: 1
UUID: LVM-tOcS1kqFV9drb0X1Vr8sxeYP0tqcrpdegyqj5lZxe45JMGlmvtqLmbLpBcenh2L3
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A.2.2. dmsetup ls 命令
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您可以使用 dmsetup ls 命令列出映射的设备的设备名称列表。您可以使用 dmsetup ls --target target_type 命令列出至少有一个指定类型的对象的设备。dmsetup ls 的其它选项请参考 dmsetup ls man page。
以下示例显示列出目前配置的映射设备的设备名称的命令。 
# dmsetup ls
testgfsvg-testgfslv3    (253:4)
testgfsvg-testgfslv2    (253:3)
testgfsvg-testgfslv1    (253:2)
VolGroup00-LogVol01     (253:1)
VolGroup00-LogVol00     (253:0)
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以下示例显示列出目前配置的镜像映射的设备名称的命令。 
# dmsetup ls --target mirror
lock_stress-grant--02.1722      (253, 34)
lock_stress-grant--01.1720      (253, 18)
lock_stress-grant--03.1718      (253, 52)
lock_stress-grant--02.1716      (253, 40)
lock_stress-grant--03.1713      (253, 47)
lock_stress-grant--02.1709      (253, 23)
lock_stress-grant--01.1707      (253, 8)
lock_stress-grant--01.1724      (253, 14)
lock_stress-grant--03.1711      (253, 27)
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LVM configurations that are stacked on multipath or other device mapper devices can be complex to sort out. The dmsetup ls command provides a --tree option that displays dependencies between devices as a tree, as in the following example. 
# dmsetup ls --tree
vgtest-lvmir (253:13)
 ├─vgtest-lvmir_mimage_1 (253:12)
 │  └─mpathep1 (253:8)
 │     └─mpathe (253:5)
 │        ├─ (8:112)
 │        └─ (8:64)
 ├─vgtest-lvmir_mimage_0 (253:11)
 │  └─mpathcp1 (253:3)
 │     └─mpathc (253:2)
 │        ├─ (8:32)
 │        └─ (8:16)
 └─vgtest-lvmir_mlog (253:4)
    └─mpathfp1 (253:10)
       └─mpathf (253:6)
          ├─ (8:128)
          └─ (8:80)
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A.2.3. dmsetup status 命令
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dmsetup status device 命令提供指定设备中每个对象的状态信息。如果您没有指定设备名称，输出会是所余目前配置的设备映射器设备信息。您可以使用 dmsetup status --target target_type 命令列出那些至少有一个指定类型的对象的设备。
以下示例显示列出在所有目前配置的映射设备中的对象状态的命令。 
# dmsetup status
testgfsvg-testgfslv3: 0 312352768 linear 
testgfsvg-testgfslv2: 0 312352768 linear 
testgfsvg-testgfslv1: 0 312352768 linear 
testgfsvg-testgfslv1: 312352768 50331648 linear 
VolGroup00-LogVol01: 0 4063232 linear 
VolGroup00-LogVol00: 0 151912448 linear
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A.2.4. dmsetup deps 命令
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dmsetup deps device 命令为指定设备的映射列表参考的设备提供（major，minor）对列表。如果您没有指定设备名称，则输出所有目前配置的设备映射器设备信息。
以下示例显示列出在所有目前配置的映射设备相依性的命令。 
# dmsetup deps
testgfsvg-testgfslv3: 1 dependencies    : (8, 16)
testgfsvg-testgfslv2: 1 dependencies    : (8, 16)
testgfsvg-testgfslv1: 1 dependencies    : (8, 16)
VolGroup00-LogVol01: 1 dependencies     : (8, 2)
VolGroup00-LogVol00: 1 dependencies     : (8, 2)
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以下示例显示只列出设备 lock_stress-grant--02.1722 相依性的命令： 
# dmsetup deps lock_stress-grant--02.1722
3 dependencies  : (253, 33) (253, 32) (253, 31)
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A.3. Device Mapper Support for the udev Device Manager
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The primary role of the udev device manager is to provide a dynamic way of setting up nodes in the /dev directory. The creation of these nodes is directed by the application of udev rules in user space. These rules are processed on udev events sent from the kernel directly as a result of adding, removing or changing particular devices. This provides a convenient and central mechanism for hotplugging support.
Besides creating the actual nodes, the udev device manager is able to create symbolic links which the user can name. This provides users the freedom to choose their own customized naming and directory structure in the/dev directory, if needed.
Each udev event contains basic information about the device being processed, such as its name, the subsystem it belongs to, the device's type, its major and minor number used, and the type of the event. Given that, and having the possibility of accessing all the information found in the /sys directory that is also accessible within udev rules, the users are able to utilize simple filters based on this information and run the rules conditionally based on this information.
The udev device manager also provides a centralized way of setting up the nodes' permissions. A user can easily add a customized set of rules to define the permissions for any device specified by any bit of information that is available while processing the event.
It is also possible to add program hooks in udev rules directly. The udev device manager can call these programs to provide further processing that is needed to handle the event. Also, the program can export environment variables as a result of this processing. Any results given can be used further in the rules as a supplementary source of information.
Any software using the udev library is able to receive and process udev events with all the information that is available, so the processing is not bound to the udev daemon only.

A.3.1. udev Integration with the Device Mapper
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In Red Hat Enterprise Linux 6, the Device Mapper provides direct support for udev integration. This synchronizes the Device Mapper with all udev processing related to Device Mapper devices, including LVM devices. The synchronization is needed since the rule application in the udev daemon is a form of parallel processing with the program that is the source of the device's changes (such as dmsetup and LVM). Without this support, it was a common problem for a user to try to remove a device that was still open and processed by udev rules as a result of a previous change event; this was particularly common when there was a very short time between changes for that device.
The Red Hat Enterprise Linux 6 release provides officially supported udev rules for Device Mapper devices in general and for LVM as well. 表 A.1 “udev Rules for Device-Mapper Devices” summarizes these rules, which are installed in /lib/udev/rules.d.
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表 A.1. udev Rules for Device-Mapper Devices
FilenameDescription
10-dm.rules
Contains basic/general Device Mapper rules and creates the symlinks in /dev/mapper with a /dev/dm-N target where N is a number assigned dynamically to a device by the kernel (/dev/dm-N is a node)
NOTE: /dev/dm-N nodes should never be used in scripts to access the device since the N number is assigned dynamically and changes with the sequence of how devices are activated. Therefore, true names in the /dev/mapper directory should be used. This layout is to support udev requirements of how nodes/symlinks should be created.
11-dm-lvm.rules
Contains rules applied for LVM devices and creates the symlinks for the volume group's logical volumes. The symlinks are created in the /dev/vgname directory with a /dev/dm-N target.
NOTE: To be consistent with the standard for naming all future rules for Device Mapper subsystems, udev rules should follow the format 11-dm-subsystem_name.rules. Any libdevmapper users providing udev rules as well should follow this standard.
13-dm-disk.rules Contains rules to be applied for all Device Mapper devices in general and creates symlinks in the /dev/disk/by-id, /dev/disk/by-uuid and the /dev/disk/by-uuid directories.
95-dm-notify.rules Contains the rule to notify the waiting process using libdevmapper (just like LVM and dmsetup). The notification is done after all previous rules are applied, to ensure any udev processing is complete. Notified process is then resumed.
69-dm-lvm-metad.rules Contains a hook to trigger an LVM scan on any newly appeared block device in the system and do any LVM autoactivation if possible. This supports the lvmetad daemon, which is set with use_lvmetad=1 in the lvm.conf file. The lvmeetad daemon and autoactivation are not supported in a clustered environment.
You can add additional customized permission rules by means of the 12-dm-permissions.rules file. This file is not installed in the /lib/udev/rules directory; it is found in the /usr/share/doc/device-mapper-version directory. The 12-dm-permissions.rules file is a template containing hints for how to set the permissions, based on some matching rules given as an example; the file contains examples for some common situations. You can edit this file and place it manually in the /etc/udev/rules.d directory where it will survive updates, so the settings will remain.
These rules set all basic variables that could be used by any other rules while processing the events.
The following variables are set in 10-dm.rules:
  • DM_NAME: Device Mapper device name
  • DM_UUID: Device Mapper device UUID
  • DM_SUSPENDED: the suspended state of Device Mapper device
  • DM_UDEV_RULES_VSN: udev rules version (this is primarily for all other rules to check that previously mentioned variables are set directly by official Device Mapper rules)
The following variables are set in 11-dm-lvm.rules:
  • DM_LV_NAME: logical volume name
  • DM_VG_NAME: volume group name
  • DM_LV_LAYER: LVM layer name
All these variables can be used in the 12-dm-permissions.rules file to define a permission for specific Device Mapper devices, as documented in the 12-dm-permissions.rules file.

A.3.2. Commands and Interfaces that Support udev
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表 A.2 “dmsetup Commands to Support udev” summarizes the dmsetup commands that support udev integration.
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表 A.2. dmsetup Commands to Support udev
CommandDescription
dmsetup udevcomplete Used to notify that udev has completed processing the rules and unlocks waiting process (called from within udev rules in 95-dm-notify.rules).
dmsetup udevcomplete_all Used for debugging purposes to manually unlock all waiting processes.
dmsetup udevcookies Used for debugging purposes, to show all existing cookies (system-wide semaphores).
dmsetup udevcreatecookie Used to create a cookie (semaphore) manually. This is useful to run more processes under one synchronization resource.
dmsetup udevreleasecookie Used to wait for all udev processing related to all processes put under that one synchronization cookie.
The dmsetup options that support udev integration are as follows.
--udevcookie
Needs to be defined for all dmsetup processes we would like to add into a udev transaction. It is used in conjunction with udevcreatecookie and udevreleasecookie: 
COOKIE=$(dmsetup udevcreatecookie)
  dmsetup command --udevcookie $COOKIE ....
  dmsetup command --udevcookie $COOKIE ....
  ....
  dmsetup command --udevcookie $COOKIE ....
dmsetup udevreleasecookie --udevcookie $COOKIE
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Besides using the --udevcookie option, you can just export the variable into an environment of the process: 
export DM_UDEV_COOKIE=$(dmsetup udevcreatecookie)
  dmsetup command ...
  dmsetup command ...
  ...
  dmsetup command ...
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--noudevrules
Disables udev rules. Nodes/symlinks will be created by libdevmapper itself (the old way). This option is for debugging purposes, if udev does not work correctly.
--noudevsync
Disables udev synchronization. This is also for debugging purposes.
For more information on the dmsetup and its options, see the dmsetup(8) man page.
The LVM commands support the following options that support udev integration:
  • --noudevrules: as for the dmsetup command, disables udev rules.
  • --noudevsync: as for the dmsetup command, disables udev synchronization.
The lvm.conf file includes the following options that support udev integration:
  • udev_rules: enables/disables udev_rules for all LVM2 commands globally.
  • udev_sync: enables/disables udev synchronization for all LVM commands globally.
For more information on the lvm.conf file options, see the inline comments in the lvm.conf file.

附录 B. LVM 配置文件
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LVM 支持多配置文件。在系统启动时，会从用环境变量 LVM_SYSTEM_DIR 指定的目录中载入 lvm.conf 配置文件，该变量在 /etc/lvm 中是默认设置。
The lvm.conf file can specify additional configuration files to load. Settings in later files override settings from earlier ones. To display the settings in use after loading all the configuration files, execute the lvmconfig command.
For information on loading additional configuration files, see 第 D.2 节 “主机标签”.

B.1. LVM 配置文件
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以下是用于 LVM 配置的文件：
/etc/lvm/lvm.conf
由工具读取的中央配置文件。
etc/lvm/lvm_hosttag.conf
For each host tag, an extra configuration file is read if it exists: lvm_hosttag.conf. If that file defines new tags, then further configuration files will be appended to the list of files to read in. For information on host tags, see 第 D.2 节 “主机标签”.
LVM profiles
An LVM profile is a set of selected customizable configuration settings that can be implemented for specific environments. The settings in an LVM profile can be used to override existing configuration. For information on LVM profiles see 第 B.3 节 “LVM Profiles”.
除了 LVM 配置文件之外，运行 LVM 的系统会包含以下可影响 LVM 系统设置的文件：
/etc/lvm/cache/.cache
设备名称过滤器缓存文件（可配置）。
/etc/lvm/backup/
自动卷组元数据备份目录（可配置）。
/etc/lvm/archive/
自动卷组元数据归档目录（可根据目录路径和归档历史记录途径进行配置）。
/var/lock/lvm
在单主机配置这，锁定文件可防止平行工具运行时破坏元数据；而在群集中，使用的群集范围的 DLM。

B.2. The lvmconfig Command
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You can display the current LVM configuration, or save the configuration to a file, with the lvmconfig command. The lvmconfig command displays the LVM configuration information after loading the /etc/lvm/lvm.conf file and any other configuration files.
There are a variety of features that the lvmconfig command provides, including the following;
  • You can dump the current lvm configuration merged with any tag configuration files.
  • You can dump all current configuration settings for which the values differ from the defaults.
  • You can dump all new configuration settings introduced in the current LVM version, in a specific LVM version.
  • You can dump all profilable configuration settings, either in their entirety or separately for command and metadata profiles. For information on LVM profiles see 第 B.3 节 “LVM Profiles”.
  • You can dump only the configuration settings for a specific version of LVM.
  • You can validate the current configuration.
For a full list of supported features and information on specifying the lvmconfig options, see the lvmconfig man page.

B.3. LVM Profiles
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An LVM profile is a set of selected customizable configuration settings that can be used to achieve certain characteristics in various environments or uses. Normally, the name of the profile should reflect that environment or use. An LVM profile overrides existing configuration.
There are two groups of LVM profiles that LVM recognizes: command profiles and metadata profiles.
  • A command profile is used to override selected configuration settings at the global LVM command level. The profile is applied at the beginning of LVM command execution and it is used throughout the time of the LVM command execution. You apply a command profile by specifying the --commandprofile ProfileName option when executing an LVM command.
  • A metadata profile is used to override selected configuration settings at the volume group/logical volume level. It is applied independently for each volume group/logical volume that is being processed. As such, each volume group/logical volume can store the profile name used in its metadata so that next time the volume group/logical volume is processed, the profile is applied automatically. If the volume group and any of its logical volumes have different profiles defined, the profile defined for the logical volume is preferred.
    • You can attach a metadata profile to a volume group or logical volume by specifying the --metadataprofile ProfileName option when you create the volume group or logical volume with the vgcreate or lvcreate command.
    • You can attach or detach a metadata profile to an existing volume group or logical volume by specifying the --metadataprofile ProfileName or the --detachprofile option of the lvchange or vgchange command.
    • You can specify the -o vg_profile and -o lv_profile output options of the vgs and lvs commands to display the metadata profile currently attached to a volume group or a logical volume.
The set of options allowed for command profiles and the set of options allowed for metadata profiles are mutually exclusive. The settings that belong to either of these two sets cannot be mixed together and the LVM tools will reject such profiles.
LVM provides a few predefined configuration profiles. The LVM profiles are stored in the /etc/lvm/profile directory by default. This location can be changed by using the profile_dir setting in the /etc/lvm/lvm.conf file. Each profile configuration is stored in ProfileName.profile file in the profile directory. When referencing the profile in an LVM command, the .profile suffix is omitted.
You can create additional profiles with different values. For this purpose, LVM provides the command_profile_template.profile file (for command profiles) and the metadata_profile_template.profile file (for metadata profiles) which contain all settings that are customizable by profiles of each type. You can copy these template profiles and edit them as needed.
Alternatively, you can use the lvmconfig command to generate a new profile for a given section of the profile file for either profile type. The following command creates a new command profile named ProfileName.profile consisting of the settings in section. 
lvmconfig --file ProfileName.profile --type profilable-command section
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The following command creates a new metadata profile named ProfileName.profile consisting of the settings in section. 
lvmconfig --file ProfileName.profile --type profilable-metadata section
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If the section is not specified, all profilable settings are reported.

B.4. lvm.conf 文件示例
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The following is a sample lvm.conf configuration file. Your configuration file may differ slightly from this one.

注意

You can generate an lvm.conf file with all of the default values set and with the comments included by running the following command: 
lvmconfig --type default --withcomments
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# This is an example configuration file for the LVM2 system.
# It contains the default settings that would be used if there was no
# /etc/lvm/lvm.conf file.
#
# Refer to 'man lvm.conf' for further information including the file layout.
#
# To put this file in a different directory and override /etc/lvm set
# the environment variable LVM_SYSTEM_DIR before running the tools.
#
# N.B. Take care that each setting only appears once if uncommenting
# example settings in this file.

# This section allows you to set the way the configuration settings are handled.
config {

    # If enabled, any LVM2 configuration mismatch is reported.
    # This implies checking that the configuration key is understood
    # by LVM2 and that the value of the key is of a proper type.
    # If disabled, any configuration mismatch is ignored and default
    # value is used instead without any warning (a message about the
    # configuration key not being found is issued in verbose mode only).
    checks = 1

    # If enabled, any configuration mismatch aborts the LVM2 process.
    abort_on_errors = 0

    # Directory where LVM looks for configuration profiles.
    profile_dir = "/etc/lvm/profile"
}

# This section allows you to configure which block devices should
# be used by the LVM system.
devices {

    # Where do you want your volume groups to appear ?
    dir = "/dev"

    # An array of directories that contain the device nodes you wish
    # to use with LVM2.
    scan = [ "/dev" ]

    # If set, the cache of block device nodes with all associated symlinks
    # will be constructed out of the existing udev database content.
    # This avoids using and opening any inapplicable non-block devices or
    # subdirectories found in the device directory. This setting is applied
    # to udev-managed device directory only, other directories will be scanned
    # fully. LVM2 needs to be compiled with udev support for this setting to
    # take effect. N.B. Any device node or symlink not managed by udev in
    # udev directory will be ignored with this setting on.
    obtain_device_list_from_udev = 1

    # If several entries in the scanned directories correspond to the
    # same block device and the tools need to display a name for device,
    # all the pathnames are matched against each item in the following
    # list of regular expressions in turn and the first match is used.
    # preferred_names = [ ]

    # Try to avoid using undescriptive /dev/dm-N names, if present.
    preferred_names = [ "^/dev/mpath/", "^/dev/mapper/mpath", "^/dev/[hs]d" ]

    # A filter that tells LVM2 to only use a restricted set of devices.
    # The filter consists of an array of regular expressions.  These
    # expressions can be delimited by a character of your choice, and
    # prefixed with either an 'a' (for accept) or 'r' (for reject).
    # The first expression found to match a device name determines if
    # the device will be accepted or rejected (ignored).  Devices that
    # don't match any patterns are accepted.

    # Be careful if there there are symbolic links or multiple filesystem 
    # entries for the same device as each name is checked separately against
    # the list of patterns.  The effect is that if the first pattern in the 
    # list to match a name is an 'a' pattern for any of the names, the device
    # is accepted; otherwise if the first pattern in the list to match a name
    # is an 'r' pattern for any of the names it is rejected; otherwise it is
    # accepted.

    # Don't have more than one filter line active at once: only one gets used.

    # Run vgscan after you change this parameter to ensure that
    # the cache file gets regenerated (see below).
    # If it doesn't do what you expect, check the output of 'vgscan -vvvv'.


    # By default we accept every block device:
    filter = [ "a/.*/" ]

    # Exclude the cdrom drive
    # filter = [ "r|/dev/cdrom|" ]

    # When testing I like to work with just loopback devices:
    # filter = [ "a/loop/", "r/.*/" ]

    # Or maybe all loops and ide drives except hdc:
    # filter =[ "a|loop|", "r|/dev/hdc|", "a|/dev/ide|", "r|.*|" ]

    # Use anchors if you want to be really specific
    # filter = [ "a|^/dev/hda8$|", "r/.*/" ]

    # Since "filter" is often overridden from command line, it is not suitable
    # for system-wide device filtering (udev rules, lvmetad). To hide devices
    # from LVM-specific udev processing and/or from lvmetad, you need to set
    # global_filter. The syntax is the same as for normal "filter"
    # above. Devices that fail the global_filter are not even opened by LVM.

    # global_filter = []

    # The results of the filtering are cached on disk to avoid
    # rescanning dud devices (which can take a very long time).
    # By default this cache is stored in the /etc/lvm/cache directory
    # in a file called '.cache'.
    # It is safe to delete the contents: the tools regenerate it.
    # (The old setting 'cache' is still respected if neither of
    # these new ones is present.)
    # N.B. If obtain_device_list_from_udev is set to 1 the list of
    # devices is instead obtained from udev and any existing .cache
    # file is removed.
    cache_dir = "/etc/lvm/cache"
    cache_file_prefix = ""

    # You can turn off writing this cache file by setting this to 0.
    write_cache_state = 1

    # Advanced settings.

    # List of pairs of additional acceptable block device types found 
    # in /proc/devices with maximum (non-zero) number of partitions.
    # types = [ "fd", 16 ]

    # If sysfs is mounted (2.6 kernels) restrict device scanning to 
    # the block devices it believes are valid.
    # 1 enables; 0 disables.
    sysfs_scan = 1

    # By default, LVM2 will ignore devices used as component paths
    # of device-mapper multipath devices.
    # 1 enables; 0 disables.
    multipath_component_detection = 1

    # By default, LVM2 will ignore devices used as components of
    # software RAID (md) devices by looking for md superblocks.
    # 1 enables; 0 disables.
    md_component_detection = 1

    # By default, if a PV is placed directly upon an md device, LVM2
    # will align its data blocks with the md device's stripe-width.
    # 1 enables; 0 disables.
    md_chunk_alignment = 1

    # Default alignment of the start of a data area in MB.  If set to 0,
    # a value of 64KB will be used.  Set to 1 for 1MiB, 2 for 2MiB, etc.
    # default_data_alignment = 1

    # By default, the start of a PV's data area will be a multiple of
    # the 'minimum_io_size' or 'optimal_io_size' exposed in sysfs.
    # - minimum_io_size - the smallest request the device can perform
    #   w/o incurring a read-modify-write penalty (e.g. MD's chunk size)
    # - optimal_io_size - the device's preferred unit of receiving I/O
    #   (e.g. MD's stripe width)
    # minimum_io_size is used if optimal_io_size is undefined (0).
    # If md_chunk_alignment is enabled, that detects the optimal_io_size.
    # This setting takes precedence over md_chunk_alignment.
    # 1 enables; 0 disables.
    data_alignment_detection = 1

    # Alignment (in KB) of start of data area when creating a new PV.
    # md_chunk_alignment and data_alignment_detection are disabled if set.
    # Set to 0 for the default alignment (see: data_alignment_default)
    # or page size, if larger.
    data_alignment = 0

    # By default, the start of the PV's aligned data area will be shifted by
    # the 'alignment_offset' exposed in sysfs.  This offset is often 0 but
    # may be non-zero; e.g.: certain 4KB sector drives that compensate for
    # windows partitioning will have an alignment_offset of 3584 bytes
    # (sector 7 is the lowest aligned logical block, the 4KB sectors start
    # at LBA -1, and consequently sector 63 is aligned on a 4KB boundary).
    # But note that pvcreate --dataalignmentoffset will skip this detection.
    # 1 enables; 0 disables.
    data_alignment_offset_detection = 1

    # If, while scanning the system for PVs, LVM2 encounters a device-mapper
    # device that has its I/O suspended, it waits for it to become accessible.
    # Set this to 1 to skip such devices.  This should only be needed
    # in recovery situations.
    ignore_suspended_devices = 0

    # During each LVM operation errors received from each device are counted.
    # If the counter of a particular device exceeds the limit set here, no
    # further I/O is sent to that device for the remainder of the respective
    # operation. Setting the parameter to 0 disables the counters altogether.
    disable_after_error_count = 0

    # Allow use of pvcreate --uuid without requiring --restorefile.
    require_restorefile_with_uuid = 1

    # Minimum size (in KB) of block devices which can be used as PVs.
    # In a clustered environment all nodes must use the same value.
    # Any value smaller than 512KB is ignored.

    # Ignore devices smaller than 2MB such as floppy drives.
    pv_min_size = 2048

    # The original built-in setting was 512 up to and including version 2.02.84.
    # pv_min_size = 512

    # Issue discards to a logical volumes's underlying physical volume(s) when
    # the logical volume is no longer using the physical volumes' space (e.g.
    # lvremove, lvreduce, etc).  Discards inform the storage that a region is
    # no longer in use.  Storage that supports discards advertise the protocol
    # specific way discards should be issued by the kernel (TRIM, UNMAP, or
    # WRITE SAME with UNMAP bit set).  Not all storage will support or benefit
    # from discards but SSDs and thinly provisioned LUNs generally do.  If set
    # to 1, discards will only be issued if both the storage and kernel provide
    # support.
    # 1 enables; 0 disables.
    issue_discards = 0
}

# This section allows you to configure the way in which LVM selects
# free space for its Logical Volumes.
allocation {

    # When searching for free space to extend an LV, the "cling"
    # allocation policy will choose space on the same PVs as the last
    # segment of the existing LV.  If there is insufficient space and a
    # list of tags is defined here, it will check whether any of them are
    # attached to the PVs concerned and then seek to match those PV tags
    # between existing extents and new extents.
    # Use the special tag "@*" as a wildcard to match any PV tag.
 
    # Example: LVs are mirrored between two sites within a single VG.
    # PVs are tagged with either @site1 or @site2 to indicate where
    # they are situated.

    # cling_tag_list = [ "@site1", "@site2" ]
    # cling_tag_list = [ "@*" ]

    # Changes made in version 2.02.85 extended the reach of the 'cling'
    # policies to detect more situations where data can be grouped
    # onto the same disks.  Set this to 0 to revert to the previous
    # algorithm.
    maximise_cling = 1

    # Set to 1 to guarantee that mirror logs will always be placed on 
    # different PVs from the mirror images.  This was the default
    # until version 2.02.85.
    mirror_logs_require_separate_pvs = 0

    # Set to 1 to guarantee that thin pool metadata will always
    # be placed on different PVs from the pool data.
    thin_pool_metadata_require_separate_pvs = 0

    # Specify the minimal chunk size (in KB) for thin pool volumes.
    # Use of the larger chunk size may improve perfomance for plain
    # thin volumes, however using them for snapshot volumes is less efficient,
    # as it consumes more space and takes extra time for copying.
    # When unset, lvm tries to estimate chunk size starting from 64KB
    # Supported values are in range from 64 to 1048576.
    # thin_pool_chunk_size = 64

    # Specify discards behavior of the thin pool volume.
    # Select one of  "ignore", "nopassdown", "passdown"
    # thin_pool_discards = "passdown"

    # Set to 0, to disable zeroing of thin pool data chunks before their
    # first use.
    # N.B. zeroing larger thin pool chunk size degrades performance.
    # thin_pool_zero = 1
}

# This section that allows you to configure the nature of the
# information that LVM2 reports.
log {

    # Controls the messages sent to stdout or stderr.
    # There are three levels of verbosity, 3 being the most verbose.
    verbose = 0

    # Set to 1 to suppress all non-essential messages from stdout.
    # This has the same effect as -qq.
    # When this is set, the following commands still produce output:
    # dumpconfig, lvdisplay, lvmdiskscan, lvs, pvck, pvdisplay, 
    # pvs, version, vgcfgrestore -l, vgdisplay, vgs.
    # Non-essential messages are shifted from log level 4 to log level 5
    # for syslog and lvm2_log_fn purposes.
    # Any 'yes' or 'no' questions not overridden by other arguments
    # are suppressed and default to 'no'.
    silent = 0

    # Should we send log messages through syslog?
    # 1 is yes; 0 is no.
    syslog = 1

    # Should we log error and debug messages to a file?
    # By default there is no log file.
    #file = "/var/log/lvm2.log"

    # Should we overwrite the log file each time the program is run?
    # By default we append.
    overwrite = 0

    # What level of log messages should we send to the log file and/or syslog?
    # There are 6 syslog-like log levels currently in use - 2 to 7 inclusive.
    # 7 is the most verbose (LOG_DEBUG).
    level = 0

    # Format of output messages
    # Whether or not (1 or 0) to indent messages according to their severity
    indent = 1

    # Whether or not (1 or 0) to display the command name on each line output
    command_names = 0

    # A prefix to use before the message text (but after the command name,
    # if selected).  Default is two spaces, so you can see/grep the severity
    # of each message.
    prefix = "  "

    # To make the messages look similar to the original LVM tools use:
    #   indent = 0
    #   command_names = 1
    #   prefix = " -- "

    # Set this if you want log messages during activation.
    # Don't use this in low memory situations (can deadlock).
    # activation = 0

    # Some debugging messages are assigned to a class and only appear
    # in debug output if the class is listed here.
    # Classes currently available:
    #   memory, devices, activation, allocation, lvmetad, metadata, cache,
    #   locking
    # Use "all" to see everything.
    debug_classes = [ "memory", "devices", "activation", "allocation",
		      "lvmetad", "metadata", "cache", "locking" ]
}

# Configuration of metadata backups and archiving.  In LVM2 when we
# talk about a 'backup' we mean making a copy of the metadata for the
# *current* system.  The 'archive' contains old metadata configurations.
# Backups are stored in a human readeable text format.
backup {

    # Should we maintain a backup of the current metadata configuration ?
    # Use 1 for Yes; 0 for No.
    # Think very hard before turning this off!
    backup = 1

    # Where shall we keep it ?
    # Remember to back up this directory regularly!
    backup_dir = "/etc/lvm/backup"

    # Should we maintain an archive of old metadata configurations.
    # Use 1 for Yes; 0 for No.
    # On by default.  Think very hard before turning this off.
    archive = 1

    # Where should archived files go ?
    # Remember to back up this directory regularly!
    archive_dir = "/etc/lvm/archive"

    # What is the minimum number of archive files you wish to keep ?
    retain_min = 10

    # What is the minimum time you wish to keep an archive file for ?
    retain_days = 30
}

# Settings for the running LVM2 in shell (readline) mode.
shell {

    # Number of lines of history to store in ~/.lvm_history
    history_size = 100
}


# Miscellaneous global LVM2 settings
global {
    # The file creation mask for any files and directories created.
    # Interpreted as octal if the first digit is zero.
    umask = 077

    # Allow other users to read the files
    #umask = 022

    # Enabling test mode means that no changes to the on disk metadata
    # will be made.  Equivalent to having the -t option on every
    # command.  Defaults to off.
    test = 0

    # Default value for --units argument
    units = "h"

    # Since version 2.02.54, the tools distinguish between powers of
    # 1024 bytes (e.g. KiB, MiB, GiB) and powers of 1000 bytes (e.g.
    # KB, MB, GB).
    # If you have scripts that depend on the old behaviour, set this to 0
    # temporarily until you update them.
    si_unit_consistency = 1

    # Whether or not to communicate with the kernel device-mapper.
    # Set to 0 if you want to use the tools to manipulate LVM metadata 
    # without activating any logical volumes.
    # If the device-mapper kernel driver is not present in your kernel
    # setting this to 0 should suppress the error messages.
    activation = 1

    # If we can't communicate with device-mapper, should we try running 
    # the LVM1 tools?
    # This option only applies to 2.4 kernels and is provided to help you
    # switch between device-mapper kernels and LVM1 kernels.
    # The LVM1 tools need to be installed with .lvm1 suffices
    # e.g. vgscan.lvm1 and they will stop working after you start using
    # the new lvm2 on-disk metadata format.
    # The default value is set when the tools are built.
    # fallback_to_lvm1 = 0

    # The default metadata format that commands should use - "lvm1" or "lvm2".
    # The command line override is -M1 or -M2.
    # Defaults to "lvm2".
    # format = "lvm2"

    # Location of proc filesystem
    proc = "/proc"

    # Type of locking to use. Defaults to local file-based locking (1).
    # Turn locking off by setting to 0 (dangerous: risks metadata corruption
    # if LVM2 commands get run concurrently).
    # Type 2 uses the external shared library locking_library.
    # Type 3 uses built-in clustered locking.
    # Type 4 uses read-only locking which forbids any operations that might 
    # change metadata.
    locking_type = 1

    # Set to 0 to fail when a lock request cannot be satisfied immediately.
    wait_for_locks = 1

    # If using external locking (type 2) and initialisation fails,
    # with this set to 1 an attempt will be made to use the built-in
    # clustered locking.
    # If you are using a customised locking_library you should set this to 0.
    fallback_to_clustered_locking = 1

    # If an attempt to initialise type 2 or type 3 locking failed, perhaps
    # because cluster components such as clvmd are not running, with this set
    # to 1 an attempt will be made to use local file-based locking (type 1).
    # If this succeeds, only commands against local volume groups will proceed.
    # Volume Groups marked as clustered will be ignored.
    fallback_to_local_locking = 1

    # Local non-LV directory that holds file-based locks while commands are
    # in progress.  A directory like /tmp that may get wiped on reboot is OK.
    locking_dir = "/var/lock/lvm"

    # Whenever there are competing read-only and read-write access requests for
    # a volume group's metadata, instead of always granting the read-only
    # requests immediately, delay them to allow the read-write requests to be
    # serviced.  Without this setting, write access may be stalled by a high
    # volume of read-only requests.
    # NB. This option only affects locking_type = 1 viz. local file-based
    # locking.
    prioritise_write_locks = 1

    # Other entries can go here to allow you to load shared libraries
    # e.g. if support for LVM1 metadata was compiled as a shared library use
    #   format_libraries = "liblvm2format1.so" 
    # Full pathnames can be given.

    # Search this directory first for shared libraries.
    #   library_dir = "/lib"

    # The external locking library to load if locking_type is set to 2.
    #   locking_library = "liblvm2clusterlock.so"

    # Treat any internal errors as fatal errors, aborting the process that
    # encountered the internal error. Please only enable for debugging.
    abort_on_internal_errors = 0

    # Check whether CRC is matching when parsed VG is used multiple times.
    # This is useful to catch unexpected internal cached volume group
    # structure modification. Please only enable for debugging.
    detect_internal_vg_cache_corruption = 0

    # If set to 1, no operations that change on-disk metadata will be permitted.
    # Additionally, read-only commands that encounter metadata in need of repair
    # will still be allowed to proceed exactly as if the repair had been 
    # performed (except for the unchanged vg_seqno).
    # Inappropriate use could mess up your system, so seek advice first!
    metadata_read_only = 0

    # 'mirror_segtype_default' defines which segtype will be used when the
    # shorthand '-m' option is used for mirroring.  The possible options are:
    #
    # "mirror" - The original RAID1 implementation provided by LVM2/DM.  It is
    # 	         characterized by a flexible log solution (core, disk, mirrored)
    #		 and by the necessity to block I/O while reconfiguring in the
    #		 event of a failure.
    #
    #		 There is an inherent race in the dmeventd failure handling
    #		 logic with snapshots of devices using this type of RAID1 that
    #		 in the worst case could cause a deadlock.
    #		   Ref: https://bugzilla.redhat.com/show_bug.cgi?id=817130#c10
    #
    # "raid1"  - This implementation leverages MD's RAID1 personality through
    # 	       	 device-mapper.  It is characterized by a lack of log options.
    #		 (A log is always allocated for every device and they are placed
    #		 on the same device as the image - no separate devices are
    #		 required.)  This mirror implementation does not require I/O
    #		 to be blocked in the kernel in the event of a failure.
    #		 This mirror implementation is not cluster-aware and cannot be
    #		 used in a shared (active/active) fashion in a cluster.
    #
    # Specify the '--type <mirror|raid1>' option to override this default
    # setting.
    mirror_segtype_default = "mirror"

    # 'raid10_segtype_default' determines the segment types used by default
    # when the '--stripes/-i' and '--mirrors/-m' arguments are both specified
    # during the creation of a logical volume.
    # Possible settings include:
    #
    # "raid10" - This implementation leverages MD's RAID10 personality through
    #            device-mapper.
    #
    # "mirror" - LVM will layer the 'mirror' and 'stripe' segment types.  It
    #            will do this by creating a mirror on top of striped sub-LVs;
    #            effectively creating a RAID 0+1 array.  This is suboptimal
    #            in terms of providing redunancy and performance.  Changing to
    #            this setting is not advised.
    # Specify the '--type <raid10|mirror>' option to override this default
    # setting.
    raid10_segtype_default = "mirror"

    # The default format for displaying LV names in lvdisplay was changed 
    # in version 2.02.89 to show the LV name and path separately.
    # Previously this was always shown as /dev/vgname/lvname even when that
    # was never a valid path in the /dev filesystem.
    # Set to 1 to reinstate the previous format.
    #
    # lvdisplay_shows_full_device_path = 0

    # Whether to use (trust) a running instance of lvmetad. If this is set to
    # 0, all commands fall back to the usual scanning mechanisms. When set to 1
    # *and* when lvmetad is running (it is not auto-started), the volume group
    # metadata and PV state flags are obtained from the lvmetad instance and no
    # scanning is done by the individual commands. In a setup with lvmetad,
    # lvmetad udev rules *must* be set up for LVM to work correctly. Without
    # proper udev rules, all changes in block device configuration will be
    # *ignored* until a manual 'pvscan --cache' is performed.
    #
    # If lvmetad has been running while use_lvmetad was 0, it MUST be stopped
    # before changing use_lvmetad to 1 and started again afterwards.
    use_lvmetad = 0

    # Full path of the utility called to check that a thin metadata device
    # is in a state that allows it to be used.
    # Each time a thin pool needs to be activated or after it is deactivated
    # this utility is executed. The activation will only proceed if the utility
    # has an exit status of 0.
    # Set to "" to skip this check.  (Not recommended.)
    # The thin tools are available as part of the device-mapper-persistent-data
    # package from https://github.com/jthornber/thin-provisioning-tools.
    #
    # thin_check_executable = "/usr/sbin/thin_check"

    # Array of string options passed with thin_check command. By default,
    # option "-q" is for quiet output.
    # With thin_check version 2.1 or newer you can add "--ignore-non-fatal-errors"
    # to let it pass through ignoreable errors and fix them later.
    #
    # thin_check_options = [ "-q" ]

    # Full path of the utility called to repair a thin metadata device
    # is in a state that allows it to be used.
    # Each time a thin pool needs repair this utility is executed.
    # See thin_check_executable how to obtain binaries.
    #
    # thin_repair_executable = "/usr/sbin/thin_repair"

    # Array of extra string options passed with thin_repair command.
    # thin_repair_options = [ "" ]

    # Full path of the utility called to dump thin metadata content.
    # See thin_check_executable how to obtain binaries.
    #
    # thin_dump_executable = "/usr/sbin/thin_dump"

    # If set, given features are not used by thin driver.
    # This can be helpful not just for testing, but i.e. allows to avoid
    # using problematic implementation of some thin feature.
    # Features:
    #   block_size
    #   discards
    #   discards_non_power_2
    #   external_origin
    #   metadata_resize
    #
    # thin_disabled_features = [ "discards", "block_size" ]
}

activation {
    # Set to 1 to perform internal checks on the operations issued to
    # libdevmapper.  Useful for debugging problems with activation.
    # Some of the checks may be expensive, so it's best to use this
    # only when there seems to be a problem.
    checks = 0

    # Set to 0 to disable udev synchronisation (if compiled into the binaries).
    # Processes will not wait for notification from udev.
    # They will continue irrespective of any possible udev processing
    # in the background.  You should only use this if udev is not running
    # or has rules that ignore the devices LVM2 creates.
    # The command line argument --nodevsync takes precedence over this setting.
    # If set to 1 when udev is not running, and there are LVM2 processes
    # waiting for udev, run 'dmsetup udevcomplete_all' manually to wake them up.
    udev_sync = 1

    # Set to 0 to disable the udev rules installed by LVM2 (if built with
    # --enable-udev_rules). LVM2 will then manage the /dev nodes and symlinks
    # for active logical volumes directly itself.
    # N.B. Manual intervention may be required if this setting is changed
    # while any logical volumes are active.
    udev_rules = 1

    # Set to 1 for LVM2 to verify operations performed by udev. This turns on
    # additional checks (and if necessary, repairs) on entries in the device
    # directory after udev has completed processing its events. 
    # Useful for diagnosing problems with LVM2/udev interactions.
    verify_udev_operations = 0

    # If set to 1 and if deactivation of an LV fails, perhaps because
    # a process run from a quick udev rule temporarily opened the device,
    # retry the operation for a few seconds before failing.
    retry_deactivation = 1

    # How to fill in missing stripes if activating an incomplete volume.
    # Using "error" will make inaccessible parts of the device return
    # I/O errors on access.  You can instead use a device path, in which 
    # case, that device will be used to in place of missing stripes.
    # But note that using anything other than "error" with mirrored 
    # or snapshotted volumes is likely to result in data corruption.
    missing_stripe_filler = "error"

    # The linear target is an optimised version of the striped target
    # that only handles a single stripe.  Set this to 0 to disable this
    # optimisation and always use the striped target.
    use_linear_target = 1

    # How much stack (in KB) to reserve for use while devices suspended
    # Prior to version 2.02.89 this used to be set to 256KB
    reserved_stack = 64

    # How much memory (in KB) to reserve for use while devices suspended
    reserved_memory = 8192

    # Nice value used while devices suspended
    process_priority = -18

    # If volume_list is defined, each LV is only activated if there is a
    # match against the list.
    #
    #   "vgname" and "vgname/lvname" are matched exactly.
    #   "@tag" matches any tag set in the LV or VG.
    #   "@*" matches if any tag defined on the host is also set in the LV or VG
    #
    # If any host tags exist but volume_list is not defined, a default
    # single-entry list containing "@*" is assumed.
    #
    # volume_list = [ "vg1", "vg2/lvol1", "@tag1", "@*" ]

    # If auto_activation_volume_list is defined, each LV that is to be
    # activated with the autoactivation option (--activate ay/-a ay) is
    # first checked against the list. There are two scenarios in which
    # the autoactivation option is used:
    #
    #   - automatic activation of volumes based on incoming PVs. If all the
    #     PVs making up a VG are present in the system, the autoactivation
    #     is triggered. This requires lvmetad (global/use_lvmetad=1) and udev
    #     to be running. In this case, "pvscan --cache -aay" is called
    #     automatically without any user intervention while processing
    #     udev events. Please, make sure you define auto_activation_volume_list
    #     properly so only the volumes you want and expect are autoactivated.
    #
    #   - direct activation on command line with the autoactivation option.
    #     In this case, the user calls "vgchange --activate ay/-a ay" or
    #     "lvchange --activate ay/-a ay" directly.
    #
    # By default, the auto_activation_volume_list is not defined and all
    # volumes will be activated either automatically or by using --activate ay/-a ay.
    #
    # N.B. The "activation/volume_list" is still honoured in all cases so even
    # if the VG/LV passes the auto_activation_volume_list, it still needs to
    # pass the volume_list for it to be activated in the end.

    # If auto_activation_volume_list is defined but empty, no volumes will be
    # activated automatically and --activate ay/-a ay will do nothing.
    #
    # auto_activation_volume_list = []

    # If auto_activation_volume_list is defined and it's not empty, only matching
    # volumes will be activated either automatically or by using --activate ay/-a ay.
    #
    #   "vgname" and "vgname/lvname" are matched exactly.
    #   "@tag" matches any tag set in the LV or VG.
    #   "@*" matches if any tag defined on the host is also set in the LV or VG
    #
    # auto_activation_volume_list = [ "vg1", "vg2/lvol1", "@tag1", "@*" ]

    # If read_only_volume_list is defined, each LV that is to be activated 
    # is checked against the list, and if it matches, it as activated
    # in read-only mode.  (This overrides '--permission rw' stored in the
    # metadata.)
    #
    #   "vgname" and "vgname/lvname" are matched exactly.
    #   "@tag" matches any tag set in the LV or VG.
    #   "@*" matches if any tag defined on the host is also set in the LV or VG
    #
    # read_only_volume_list = [ "vg1", "vg2/lvol1", "@tag1", "@*" ]

    # Each LV can have an 'activation skip' flag stored persistently against it.
    # During activation, this flag is used to decide whether such an LV is skipped.
    # The 'activation skip' flag can be set during LV creation and by default it
    # is automatically set for thin snapshot LVs. The 'auto_set_activation_skip'
    # enables or disables this automatic setting of the flag while LVs are created.
    # auto_set_activation_skip = 1

    # For RAID or 'mirror' segment types, 'raid_region_size' is the
    # size (in kiB) of each:
    # - synchronization operation when initializing
    # - each copy operation when performing a 'pvmove' (using 'mirror' segtype)
    # This setting has replaced 'mirror_region_size' since version 2.02.99
    raid_region_size = 512

    # Setting to use when there is no readahead value stored in the metadata.
    #
    # "none" - Disable readahead.
    # "auto" - Use default value chosen by kernel.
    readahead = "auto"

    # 'raid_fault_policy' defines how a device failure in a RAID logical
    # volume is handled.  This includes logical volumes that have the following
    # segment types: raid1, raid4, raid5*, and raid6*.
    #
    # In the event of a failure, the following policies will determine what
    # actions are performed during the automated response to failures (when
    # dmeventd is monitoring the RAID logical volume) and when 'lvconvert' is
    # called manually with the options '--repair' and '--use-policies'.
    #
    # "warn"	- Use the system log to warn the user that a device in the RAID
    # 		  logical volume has failed.  It is left to the user to run
    #		  'lvconvert --repair' manually to remove or replace the failed
    #		  device.  As long as the number of failed devices does not
    #		  exceed the redundancy of the logical volume (1 device for
    #		  raid4/5, 2 for raid6, etc) the logical volume will remain
    #		  usable.
    #
    # "allocate" - Attempt to use any extra physical volumes in the volume
    # 		  group as spares and replace faulty devices.
    #
    raid_fault_policy = "warn"

    # 'mirror_image_fault_policy' and 'mirror_log_fault_policy' define
    # how a device failure affecting a mirror (of "mirror" segment type) is
    # handled.  A mirror is composed of mirror images (copies) and a log.
    # A disk log ensures that a mirror does not need to be re-synced
    # (all copies made the same) every time a machine reboots or crashes.
    #
    # In the event of a failure, the specified policy will be used to determine
    # what happens. This applies to automatic repairs (when the mirror is being
    # monitored by dmeventd) and to manual lvconvert --repair when
    # --use-policies is given.
    #
    # "remove" - Simply remove the faulty device and run without it.  If
    #            the log device fails, the mirror would convert to using
    #            an in-memory log.  This means the mirror will not
    #            remember its sync status across crashes/reboots and
    #            the entire mirror will be re-synced.  If a
    #            mirror image fails, the mirror will convert to a
    #            non-mirrored device if there is only one remaining good
    #            copy.
    #
    # "allocate" - Remove the faulty device and try to allocate space on
    #            a new device to be a replacement for the failed device.
    #            Using this policy for the log is fast and maintains the
    #            ability to remember sync state through crashes/reboots.
    #            Using this policy for a mirror device is slow, as it
    #            requires the mirror to resynchronize the devices, but it
    #            will preserve the mirror characteristic of the device.
    #            This policy acts like "remove" if no suitable device and
    #            space can be allocated for the replacement.
    #
    # "allocate_anywhere" - Not yet implemented. Useful to place the log device
    #            temporarily on same physical volume as one of the mirror
    #            images. This policy is not recommended for mirror devices
    #            since it would break the redundant nature of the mirror. This
    #            policy acts like "remove" if no suitable device and space can
    #            be allocated for the replacement.

    mirror_log_fault_policy = "allocate"
    mirror_image_fault_policy = "remove"

    # 'snapshot_autoextend_threshold' and 'snapshot_autoextend_percent' define
    # how to handle automatic snapshot extension. The former defines when the
    # snapshot should be extended: when its space usage exceeds this many
    # percent. The latter defines how much extra space should be allocated for
    # the snapshot, in percent of its current size.
    #
    # For example, if you set snapshot_autoextend_threshold to 70 and
    # snapshot_autoextend_percent to 20, whenever a snapshot exceeds 70% usage,
    # it will be extended by another 20%. For a 1G snapshot, using up 700M will
    # trigger a resize to 1.2G. When the usage exceeds 840M, the snapshot will
    # be extended to 1.44G, and so on.
    #
    # Setting snapshot_autoextend_threshold to 100 disables automatic
    # extensions. The minimum value is 50 (A setting below 50 will be treated
    # as 50).

    snapshot_autoextend_threshold = 100
    snapshot_autoextend_percent = 20

    # 'thin_pool_autoextend_threshold' and 'thin_pool_autoextend_percent' define
    # how to handle automatic pool extension. The former defines when the
    # pool should be extended: when its space usage exceeds this many
    # percent. The latter defines how much extra space should be allocated for
    # the pool, in percent of its current size.
    #
    # For example, if you set thin_pool_autoextend_threshold to 70 and
    # thin_pool_autoextend_percent to 20, whenever a pool exceeds 70% usage,
    # it will be extended by another 20%. For a 1G pool, using up 700M will
    # trigger a resize to 1.2G. When the usage exceeds 840M, the pool will
    # be extended to 1.44G, and so on.
    #
    # Setting thin_pool_autoextend_threshold to 100 disables automatic
    # extensions. The minimum value is 50 (A setting below 50 will be treated
    # as 50).

    thin_pool_autoextend_threshold = 100
    thin_pool_autoextend_percent = 20

    # While activating devices, I/O to devices being (re)configured is
    # suspended, and as a precaution against deadlocks, LVM2 needs to pin
    # any memory it is using so it is not paged out.  Groups of pages that
    # are known not to be accessed during activation need not be pinned
    # into memory.  Each string listed in this setting is compared against
    # each line in /proc/self/maps, and the pages corresponding to any
    # lines that match are not pinned.  On some systems locale-archive was
    # found to make up over 80% of the memory used by the process.
    # mlock_filter = [ "locale/locale-archive", "gconv/gconv-modules.cache" ]

    # Set to 1 to revert to the default behaviour prior to version 2.02.62
    # which used mlockall() to pin the whole process's memory while activating
    # devices.
    use_mlockall = 0

    # Monitoring is enabled by default when activating logical volumes.
    # Set to 0 to disable monitoring or use the --ignoremonitoring option.
    monitoring = 1

    # When pvmove or lvconvert must wait for the kernel to finish
    # synchronising or merging data, they check and report progress
    # at intervals of this number of seconds.  The default is 15 seconds.
    # If this is set to 0 and there is only one thing to wait for, there
    # are no progress reports, but the process is awoken immediately the
    # operation is complete.
    polling_interval = 15
}


####################
# Advanced section #
####################

# Metadata settings
#
# metadata {
    # Default number of copies of metadata to hold on each PV.  0, 1 or 2.
    # You might want to override it from the command line with 0 
    # when running pvcreate on new PVs which are to be added to large VGs.

    # pvmetadatacopies = 1

    # Default number of copies of metadata to maintain for each VG.
    # If set to a non-zero value, LVM automatically chooses which of
    # the available metadata areas to use to achieve the requested
    # number of copies of the VG metadata.  If you set a value larger
    # than the the total number of metadata areas available then
    # metadata is stored in them all.
    # The default value of 0 ("unmanaged") disables this automatic
    # management and allows you to control which metadata areas
    # are used at the individual PV level using 'pvchange
    # --metadataignore y/n'.

    # vgmetadatacopies = 0

    # Approximate default size of on-disk metadata areas in sectors.
    # You should increase this if you have large volume groups or
    # you want to retain a large on-disk history of your metadata changes.

    # pvmetadatasize = 255

    # List of directories holding live copies of text format metadata.
    # These directories must not be on logical volumes!
    # It's possible to use LVM2 with a couple of directories here,
    # preferably on different (non-LV) filesystems, and with no other 
    # on-disk metadata (pvmetadatacopies = 0). Or this can be in
    # addition to on-disk metadata areas.
    # The feature was originally added to simplify testing and is not
    # supported under low memory situations - the machine could lock up.
    #
    # Never edit any files in these directories by hand unless you
    # you are absolutely sure you know what you are doing! Use
    # the supplied toolset to make changes (e.g. vgcfgrestore).

    # dirs = [ "/etc/lvm/metadata", "/mnt/disk2/lvm/metadata2" ]
#}

# Event daemon
#
dmeventd {
    # mirror_library is the library used when monitoring a mirror device.
    #
    # "libdevmapper-event-lvm2mirror.so" attempts to recover from
    # failures.  It removes failed devices from a volume group and
    # reconfigures a mirror as necessary. If no mirror library is
    # provided, mirrors are not monitored through dmeventd.

    mirror_library = "libdevmapper-event-lvm2mirror.so"

    # snapshot_library is the library used when monitoring a snapshot device.
    #
    # "libdevmapper-event-lvm2snapshot.so" monitors the filling of
    # snapshots and emits a warning through syslog when the use of
    # the snapshot exceeds 80%. The warning is repeated when 85%, 90% and
    # 95% of the snapshot is filled.

    snapshot_library = "libdevmapper-event-lvm2snapshot.so"

    # thin_library is the library used when monitoring a thin device.
    #
    # "libdevmapper-event-lvm2thin.so" monitors the filling of
    # pool and emits a warning through syslog when the use of
    # the pool exceeds 80%. The warning is repeated when 85%, 90% and
    # 95% of the pool is filled.

    thin_library = "libdevmapper-event-lvm2thin.so"

    # Full path of the dmeventd binary.
    #
    # executable = "/sbin/dmeventd"
}
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附录 C. LVM Selection Criteria
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As of Red Hat Enterpise Linux release 6.6, many LVM reporting commmands accept the -S or --select option to define selection criteria for those commands. As of Red Hat Enterprise Linux release 6.7, many processing commands support selection criteria as well. These two categories of commands for which you can define selection criteria are defined as follows:
  • Reporting commands — Display only the lines that satisfy the selection criteria. Examples of reporting commands for which you can define selection criteria include pvs, vgs, lvs, pvdisplay, vgdisplay, lvdisplay, lvm devtypes, and dmsetup info -c.
    Specifying the -o selected option in addition to the -S option displays all rows and adds a "selected" column that shows 1 if the row matches the selection criteria and 0 if it does not.
  • Processing commands — Process only the items that satisfy the selection criteria. Examples of processing commands for which you can define selection criteria include pvchange, vgchange, lvchange, vgimport, vgexport, vgremove, and lvremove.
Selection criteria are a set of statements that use comparison operators to define the valid values for particular fields to display or process. The selected fields are, in turn, combined by logical and grouping operators.
When specifying which fields to display using selection criteria, there is no requirement for the field which is in the selection criteria to be displayed. The selection criteria can contain one set of fields while the output can contain a different set of fields.
  • For a listing of available fields for the various LVM components, see 第 C.3 节 “Selection Criteria Fields”.
  • For a listing of allowed operators, see 第 C.2 节 “Selection Criteria Operators”. The operators are also provided on the lvm(8) man page.
  • You can also see full sets of fields and possible operators by specifying the help (or ?) keyword for the -S/--select option of a reporting commands. For example, the following command displays the fields and possible operators for the lvs command. 
    # lvs -S help
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For the Red Hat Enterprise Linux 6.8 release, you can specify time values as selection criteria for fields with a field type of time. For information on specifying time values, see 第 C.3.1 节 “Specifying Time Values”.

C.1. Selection Criteria Field Types
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The fields you specify for selection criteria are of a particular type. The help output for each field display the field type enclosed in brackets. The following help output examples show the output indicating the field types string, string_list, number, percent, and size. 
lv_name             - Name. LVs created for internal use are enclosed in brackets.[string]
lv_role             - LV role. [string list]
raid_mismatch_count - For RAID, number of mismatches found or repaired. [number]
copy_percent        - For RAID, mirrors and pvmove, current percentage in-sync. [percent]
lv_size             - Size of LV in current units. [size]
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表 C.1 “Selection Criteria Field Types” describes the selection criteria field types
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表 C.1. Selection Criteria Field Types
Field TypeDescription
number Non-negative integer value.
size Floating point value with units, 'm' unit used by default if not specified.
percent Non-negative integer with or without % suffix.
string Characters quoted by ' or " or unquoted.
string list Strings enclosed by [ ] or { } and elements delimited by either "all items must match" or "at least one item must match" operator.
The values you specify for a field can be the following:
  • Concrete values of the field type
  • Regular expressions that include any fields of the string field type, such as "+~" operator.
  • Reserved values; for example -1, unknown, undefined, undef are all keywords to denote an undefined numeric value.
  • Defined synonyms for the field values, which can be used in selection criteria for values just as for their original values. For a listing of defined synonyms for field values, see 表 C.14 “Selection Criteria Synonyms”.

C.2. Selection Criteria Operators
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表 C.2 “Selection Criteria Grouping Operators” describes the selection criteria grouping operators.
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表 C.2. Selection Criteria Grouping Operators
Grouping OperatorDescription
( ) Used for grouping statements
[ ] Used to group strings into a string list (exact match)
{ } Used to group strings into a string list (subset match)
表 C.3 “Selection Criteria Comparison Operators” describes the selection criteria comparison operators and the field types with which they can be used.
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表 C.3. Selection Criteria Comparison Operators
Comparison OperatorDescriptionField Type
=~ Matching regular expression regex
!~ Not matching regular expression. regex
= Equal to number, size, percent, string, string list
!= Not equal to number, size, percent, string, string list
>= Greater than or equal to number, size, percent
> Greater than number, size, percent
<= Less than or equal to number, size, percent
< Less than number, size, percent
表 C.4 “Selection Criteria Logical and Grouping Operators” describes the selection criteria logical and grouping operators.
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表 C.4. Selection Criteria Logical and Grouping Operators
Logical and Grouping OperatorDescription
&& All fields must match
, All fields must match (same as &&)
|| At least one field must match
# At least one field must match (same as ||)
! Logical negation
( Left parenthesis (grouping operator)
) Right parenthesis (grouping operator)
[ List start (grouping operator)
] List end (grouping operator)
{ List subset start (grouping operator)
} List subset end (grouping operator)

C.3. Selection Criteria Fields
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This section describes the logical and physical volume selection criteria fields you can specify.
表 C.5 “Logical Volume Fields” describes the logical volume fields and their field types.
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表 C.5. Logical Volume Fields
Logical Volume FieldDescriptionField Type
lv_uuid Unique identifier string
lv_name Name (logical volumes created for internal use are enclosed in brackets) string
lv_full_name Full name of logical volume including its volume group, namely VG/LV string
lv_path Full pathname for logical volume (blank for internal logical volumes) string
lv_dm_path Internal device mapper pathname for logical volume (in /dev/mapper directory) string
lv_parent For logical volumes that are components of another logical volume, the parent logical volume string
lv_layout logical volume layout string list
lv_role logical volume role string list
lv_initial_image_sync Set if mirror/RAID images underwent initial resynchronization number
lv_image_synced Set if mirror/RAID image is synchronized number
lv_merging Set if snapshot logical volume is being merged to origin number
lv_converting Set if logical volume is being converted number
lv_allocation_policy logical volume allocation policy string
lv_allocation_locked Set if logical volume is locked against allocation changes number
lv_fixed_minor Set if logical volume has fixed minor number assigned number
lv_merge_failed Set if snapshot merge failed number
lv_snapshot_invalid Set if snapshot logical volume is invalid number
lv_skip_activation Set if logical volume is skipped on activation number
lv_when_full For thin pools, behavior when full string
lv_active Active state of the logical volume string
lv_active_locally Set if the logical volume is active locally number
lv_active_remotely Set if the logical volume is active remotely number
lv_active_exclusively Set if the logical volume is active exclusively number
lv_major Persistent major number or -1 if not persistent number
lv_minor Persistent minor number or -1 if not persistent number
lv_read_ahead Read ahead setting in current units size
lv_size Size of logical volume in current units size
lv_metadata_size For thin and cache pools, the size of the logical volume that holds the metadata size
seg_count Number of segments in logical volume number
origin For snapshots, the origin device of this logical volume string
origin_size For snapshots, the size of the origin device of this logical volume size
data_percent For snapshot and thin pools and volumes, the percentage full if logical volume is active percent
snap_percent For snapshots, the percentage full if logical volume is active percent
metadata_percent For thin pools, the percentage of metadata full if logical volume is active percent
copy_percent For RAID, mirrors and pvmove, current percentage in-sync percent
sync_percent For RAID, mirrors and pvmove, current percentage in-sync percent
raid_mismatch_count For RAID, number of mismatches found or repaired number
raid_sync_action For RAID, the current synchronization action being performed string
raid_write_behind For RAID1, the number of outstanding writes allowed to writemostly devices number
raid_min_recovery_rate For RAID1, the minimum recovery I/O load in kiB/sec/disk number
raid_max_recovery_rate For RAID1, the maximum recovery I/O load in kiB/sec/disk number
move_pv For pvmove, source physical volume of temporary logical volume created by pvmove string
convert_lv For lvconvert, name of temporary logical volume created by lvconvert string
mirror_log For mirrors, the logical volume holding the synchronization log string
data_lv For thin and cache pools, the logical volume holding the associated data string
metadata_lv For thin and cache pools, the logical volume holding the associated metadata string
pool_lv For thin volumes, the thin pool logical volume for this volume string
lv_tags Tags, if any string list
lv_profile Configuration profile attached to this logical volume string
lv_time Creation time of the logical volume, if known string
lv_host Creation host of the logical volume, if known string
lv_modules Kernel device-mapper modules required for this logical volume string list
表 C.6 “Logical Volume Device Combined Info and Status Fields” describes the logical volume device fields that combine both logical device info and logical device status.
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表 C.6. Logical Volume Device Combined Info and Status Fields
Logical Volume FieldDescriptionField Type
lv_attr Selects according to both logical volume device info as well as logical volume status. string
表 C.7 “Logical Volume Device Info Fields” describes the logical volume device info fields and their field types.
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表 C.7. Logical Volume Device Info Fields
Logical Volume FieldDescriptionField Type
lv_kernel_major Currently assigned major number or -1 if logical volume is not active number
lv_kernel_minor Currently assigned minor number or -1 if logical volume is not active number
lv_kernel_read_ahead Currently-in-use read ahead setting in current units size
lv_permissions logical volume permissions string
lv_suspended Set if logical volume is suspended number
lv_live_table Set if logical volume has live table present number
lv_inactive_table Set if logical volume has inactive table present number
lv_device_open Set if logical volume device is open number
表 C.8 “Logical Volume Device Status Fields” describes the logical volume device status fields and their field types.
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表 C.8. Logical Volume Device Status Fields
Logical Volume FieldDescriptionField Type
cache_total_blocks Total cache blocks number
cache_used_blocks Used cache blocks number
cache_dirty_blocks Dirty cache blocks number
cache_read_hits Cache read hits number
cache_read_misses Cache read misses number
cache_write_hits Cache write hits number
cache_write_misses Cache write misses number
lv_health_status logical volume health status string
表 C.9 “Physical Volume Label Fields” describes the physical volume label fields and their field types.
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表 C.9. Physical Volume Label Fields
Physical Volume FieldDescriptionField Type
pv_fmt Type of metadata string
pv_uuid Unique identifier string
dev_size Size of underlying device in current units size
pv_name Name string
pv_mda_free Free metadata area space on this device in current units size
pv_mda_size Size of smallest metadata area on this device in current units size
表 C.5 “Logical Volume Fields” describes the physical volume fields and their field types.
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表 C.10. Pysical Volume Fields
Physical Volume FieldDescriptionField Type
pe_start Offset to the start of data on the underlying device number
pv_size Size of physical volume in current units size
pv_free Total amount of unallocated space in current units size
pv_used Total amount of allocated space in current units size
pv_attr Various attributes string
pv_allocatable Set if this device can be used for allocation number
pv_exported Set if this device is exported number
pv_missing Set if this device is missing in system number
pv_pe_count Total number of physical extents number
pv_pe_alloc_count Total number of allocated physical extents number
pv_tags Tags, if any string list
pv_mda_count Number of metadata areas on this device number
pv_mda_used_count Number of metadata areas in use on this device number
pv_ba_start Offset to the start of PV Bootloader Area on the underlying device in current units size
pv_ba_size Size of PV Bootloader Area in current units size
表 C.11 “Volume Group Fields” describes the volume group fields and their field types.
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表 C.11. Volume Group Fields
Volume Group FieldDescriptionField Type
vg_fmt Type of metadata string
vg_uuid Unique identifier string
vg_name Name string
vg_attr Various attributes string
vg_permissions Volume group permissions string
vg_extendable Set if volume group is extendable number
vg_exported Set if volume group is exported number
vg_partial Set if volume group is partial number
vg_allocation_policy Volume group allocation policy string
vg_clustered Set if volume group is clustered number
vg_size Total size of volume group in current units size
vg_free Total amount of free space in current units size
vg_sysid System ID of the volume group indicating which host owns it string
vg_systemid System ID of the volume group indicating which host owns it string
vg_extent_size Size of physical extents in current units size
vg_extent_count Total number of physical extents number
vg_free_count Total number of unallocated physical extents number
max_lv Maximum number of logical volumes allowed in volume group or 0 if unlimited number
max_pv Maximum number of physical volumes allowed in volume group or 0 if unlimited number
pv_count Number of physical volumes number
lv_count Number of logical volumes number
snap_count Number of snapshots number
vg_seqno Revision number of internal metadata — incremented whenever it changes number
vg_tags Tags, if any string list
vg_profile Configuration profile attached to this volume group string
vg_mda_count Number of metadata areas on this volume group number
vg_mda_used_count Number of metadata areas in use on this volume group number
vg_mda_free Free metadata area space for this volume group in current units size
vg_mda_size Size of smallest metadata area for this volume group in current units size
vg_mda_copies Target number of in use metadata areas in the volume group number
表 C.12 “Logical Volume Segment Fields” describes the logical volume segment fields and their field types.
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表 C.12. Logical Volume Segment Fields
Logical Volume Segment FieldDescriptionField Type
segtype Type of logical volume segment string
stripes Number of stripes or mirror legs number
stripesize For stripes, amount of data placed on one device before switching to the next size
stripe_size For stripes, amount of data placed on one device before switching to the next size
regionsize For mirrors, the unit of data copied when synchronizing devices size
region_size For mirrors, the unit of data copied when synchronizing devices size
chunksize For snapshots, the unit of data used when tracking changes size
chunk_size For snapshots, the unit of data used when tracking changes size
thin_count For thin pools, the number of thin volumes in this pool number
discards For thin pools, how discards are handled string
cachemode For cache pools, how writes are cached string
zero For thin pools, if zeroing is enabled number
transaction_id For thin pools, the transaction id number
thin_id For thin volumes, the thin device id number
seg_start Offset within the logical volume to the start of the segment in current units size
seg_start_pe Offset within the logical volume to the start of the segment in physical extents. number
seg_size Size of segment in current units size
seg_size_pe Size of segment in physical extents size
seg_tags Tags, if any string list
seg_pe_ranges Ranges of physical extents of underlying devices in command line format string
devices Underlying devices used with starting extent numbers string
seg_monitor dmeventd monitoring status of the segment string
cache_policy The cache policy (cached segments only) string
cache_settings Cache settings/parameters (cached segments only) string list
表 C.13 “Pysical Volume Segment Fields” describes the physical volume segment fields and their field types.
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表 C.13. Pysical Volume Segment Fields
Physical Volume Segment FieldDescriptionField Type
pvseg_start Physical extent number of start of segment number
pvseg_size Number of extents in segment number
表 C.14 “Selection Criteria Synonyms” lists the synonyms you can use for field values. These synonyms can be used in selection criteria as well as for values just like their original values. In this table, a field value of "" indicates a blank string, which can be matched by specifying -S 'field_name=""'.
In this table, a field indicated by 0 or 1 indicates a binary value. You can specify a --binary option for reporting tools which causes binary fields to display 0 or 1 instead of what is indicated in this table as "some text" or "".
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表 C.14. Selection Criteria Synonyms
FieldField ValueSynonyms
pv_allocatable allocatable 1
pv_allocatable "" 0
pv_exported exported 1
pv_exported "" 0
pv_missing missing 1
pv_missing "" 0
vg_extendable extendable 1
vg_extendable "" 0
vg_exported exported 1
vg_exported "" 0
vg_partial partial 1
vg_partial "" 0
vg_clustered clustered 1
vg_clustered "" 0
vg_permissions writeable rw, read-write
vg_permissions read-only r, ro
vg_mda_copies unmanaged unknown, undefined, undef, -1
lv_initial_image_sync initial image sync sync, 1
lv_initial_image_sync "" 0
lv_image_synced image synced synced, 1
lv_image_synce "" 0
lv_merging merging 1
lv_merging "" 0
lv_converting converting 1
lv_converting "" 0
lv_allocation_locked allocation locked locked, 1
lv_allocation_locked "" 0
lv_fixed_minor fixed minor fixed, 1
lv_fixed_minor "" 0
lv_active_locally active locally active, locally, 1
lv_active_locally "" 0
lv_active_remotely active remotely active, remotely, 1
lv_active_remotely "" 0
lv_active_exclusively active exclusively active, exclusively, 1
lv_active_exclusively "" 0
lv_merge_failed merge failed failed, 1
lv_merge_failed "" 0
lv_snapshot_invalid snapshot invalid invalid, 1
lv_snapshot_invalid "" 0
lv_suspended suspended 1
lv_suspended "" 0
lv_live_table live table present live table, live, 1
lv_live_table "" 0
lv_inactive_table inactive table present inactive table, inactive, 1
lv_inactive_table "" 0
lv_device_open open 1
lv_device_open "" 0
lv_skip_activation skip activation skip, 1
lv_skip_activation "" 0
zero zero 1
zero "" 0
lv_permissions writeable rw, read-write
lv_permissions read-only r, ro
lv_permissions read-only-override ro-override, r-override, R
lv_when_full error error when full, error if no space
lv_when_full queue queue when full, queue if no space
lv_when_full "" undefined
cache_policy "" undefined
seg_monitor "" undefined
lv_health_status "" undefined

C.3.1. Specifying Time Values
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When specifying time values for LVM selection, you can use either a standardized time specification format or a more free-form specification, as described in 第 C.3.1.1 节 “Standard time selection format” and 第 C.3.1.2 节 “Freeform time selection format”.
You can specify the way time values are displayed with the report/time format configuration option in the /etc/lvm/lvm.conf configuration file. Information on specifying this option is provided in the lvm.conf file.
When specifying time values, you can use the comparison operator aliases since, after, until, and before, as described in 表 C.3 “Selection Criteria Comparison Operators”.
C.3.1.1. Standard time selection format
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You can specify time values for LVM selection in the following format. 
date time timezone
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表 C.15 “Time Specification Formats” summarizes the formats you can use when specifying these time values.
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表 C.15. Time Specification Formats
FieldField Value
date
YYYY-MM-DD
YYYY-MM, auto DD=1
YYYY, auto MM=01 and DD=01
time
hh:mm:ss
hh:mm, auto ss=0
hh, auto mm=0, auto ss=0
timezone (always with + or - sign)
+hh:mm or -hh:mm
+hh or -hh
The full date/time specification is YYYY-MM-DD hh:mm:ss. Users are able to leave date/time parts from right to left. Whenever these parts are left out, a range is assumed automatically with second granularity. For example:
  • "2015-07-07 9:51" means range of "2015-07-07 9:51:00" - "2015-07-07 9:51:59"
  • "2015-07" means range of "2015-07-01 0:00:00" - "2015-07-31 23:59:59"
  • "2015" means range of "2015-01-01 0:00:00" - "2015-12-31 23:59:59"
The following examples show the date/time specification as used in selection criteria. 
lvs -S 'time since "2015-07-07 9:51"'
lvs -S 'time = "2015-07""
lvs -S 'time = "2015"'
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C.3.1.2. Freeform time selection format
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You can specify the date/time specification in LVM selection criteria using the following entitles.
  • weekday names ("Sunday" - "Saturday" or abbreviated as "Sun" - "Sat")
  • labels for points in time ("noon", "midnight")
  • labels for a day relative to current day ("today", "yesterday")
  • points back in time with relative offset from today (N is a number)
  • ( "N" "seconds"/"minutes"/"hours"/"days"/"weeks"/"years" "ago")
  • ( "N" "secs"/"mins"/"hrs" ... "ago")
  • ( "N" "s"/"m"/"h" ... "ago")
  • time specification either in hh:mm:ss format or with AM/PM suffixes
  • month names ("January" - "December" or abbreviated as "Jan" - "Dec")
The following examples the show the freeform date/time specificaiton as used in selection criteria. 
lvs -S 'time since "yesterday 9AM"'
lvs -S 'time since "Feb 3 years 2 months ago"'
lvs -S 'time = "February 2015"'
lvs -S 'time since "Jan 15 2015" &&  time until yesterday'
lvs -S 'time since "today 6AM"'
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C.4. Selection Criteria Display Examples
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This section provides a series of examples showing how to use selection criteria for LVM display commands. The examples in this section use a system configured with LVM volumes that yield the following output when selection criteria are not used. 
# lvs -a -o+layout,role
  LV              VG Attr       LSize   Pool Origin Data%  Meta%  Layout      Role
  root            f1 -wi-ao----   9.01g                           linear      public
  swap            f1 -wi-ao---- 512.00m                           linear      public
  [lvol0_pmspare] vg ewi-------   4.00m                           linear      private,   \
                                                                              pool,spare
  lvol1           vg Vwi-a-tz--   1.00g pool        0.00          thin,sparse public
  lvol2           vg Vwi-a-tz--   1.00g pool        0.00          thin,sparse public,    \
                                                                              origin,    \
                                                                              thinorigin
  lvol3           vg Vwi---tz-k   1.00g pool lvol2                thin,sparse public,    \
                                                                              snapshot,  \
                                                                              thinsnapshot
  pool            vg twi-aotz-- 100.00m             0.00   1.07   thin,pool   private
  [pool_tdata]    vg Twi-ao---- 100.00m                           linear      private,   \
                                                                              thin,pool, \
                                                                              data
  [pool_tmeta]    vg ewi-ao----   4.00m                           linear      private,   \
                                                                              thin,pool, \
                                                                              metadata
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The following command displays all logical volumes with "lvol[13]" in their name, using a regular expression to specify this. 
# lvs -a -o+layout,role -S 'lv_name=~lvol[13]'
  LV    VG   Attr       LSize Pool Origin Data%  Layout      Role                        
  lvol1 vg   Vwi-a-tz-- 1.00g pool        0.00   thin,sparse public                      
  lvol3 vg   Vwi---tz-k 1.00g pool lvol2         thin,sparse public,snapshot,thinsnapshot
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The following command displays all logical volumes greater than 500m in size. 
# lvs -a -o+layout,role -S 'lv_size>500m'
  LV    VG Attr       LSize   Pool Origin Data%  Layout      Role                        
  root  f1 -wi-ao----   9.01g                    linear      public                      
  swap  f1 -wi-ao---- 512.00m                    linear      public                      
  lvol1 vg Vwi-a-tz--   1.00g pool        0.00   thin,sparse public                      
  lvol2 vg Vwi-a-tz--   1.00g pool        0.00   thin,sparse public,origin,thinorigin    
  lvol3 vg Vwi---tz-k   1.00g pool lvol2         thin,sparse public,snapshot,           \
                                                             thinsnapshot
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The following command displays all logical volumes that include thin as a logical volume role, indicating that the logical volume is used in constructing a thin pool. This example uses braces ({}) to indicate a subset in the display. 
# lvs -a -o+layout,role -S 'lv_role={thin}'
  LV           VG   Attr       LSize   Layout     Role                      
  [pool_tdata] vg   Twi-ao---- 100.00m linear     private,thin,pool,data    
  [pool_tmeta] vg   ewi-ao----   4.00m linear     private,thin,pool,metadata
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The following command displays all usable top-level logical volumes, which are the logical volumes with a role of "public". If you do not specify braces ({}) in a string list to indicate a subset, it is assumed by default; specifying lv_role=public is equivalent to specifying lv_role={public}. 
# lvs -a -o+layout,role -S 'lv_role=public' 
  LV    VG Attr       LSize   Pool Origin Data%  Layout      Role                        
  root  f1 -wi-ao----   9.01g                    linear      public                      
  swap  f1 -wi-ao---- 512.00m                    linear      public                      
  lvol1 vg Vwi-a-tz--   1.00g pool        0.00   thin,sparse public                      
  lvol2 vg Vwi-a-tz--   1.00g pool        0.00   thin,sparse public,origin,thinorigin 
  lvol3 vg Vwi---tz-k   1.00g pool lvol2         thin,sparse public,snapshot,thinsnapshot
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The following command displays all logical volumes with a thin layout. 
# lvs -a -o+layout,role -S 'lv_layout={thin}'
  LV    VG Attr       LSize   Pool Origin Data% Meta% Layout      Role 
  lvol1 vg Vwi-a-tz--   1.00g pool        0.00        thin,sparse public 
  lvol2 vg Vwi-a-tz--   1.00g pool        0.00        thin,sparse public,origin,          \
                                                                  thinorigin    
  lvol3 vg Vwi---tz-k   1.00g pool lvol2              thin,sparse public,snapshot,        \
                                                                  thinsnapshot
  pool  vg twi-aotz-- 100.00m             0.00  1.07  thin,pool   private
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The following command displays all logical volumes with a layout field that matches "sparse,thin" exactly. Note that it is not necessary to specify the string list members for the match to be positive. 
# lvs -a -o+layout,role -S 'lv_layout=[sparse,thin]'
  LV    VG   Attr       LSize Pool Origin Data%  Layout      Role                        
  lvol1 vg   Vwi-a-tz-- 1.00g pool        0.00   thin,sparse public                      
  lvol2 vg   Vwi-a-tz-- 1.00g pool        0.00   thin,sparse public,origin,thinorigin    
  lvol3 vg   Vwi---tz-k 1.00g pool lvol2         thin,sparse public,snapshot,thinsnapshot
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The following command displays the logical volume names of the logical volumes that are thin, sparse logical volumes. Note that the list of fields used for selection criteria do not need to be the same as the list of fields to display. 
# lvs -a -o lv_name -S 'lv_layout=[sparse,thin]'
  LV   
  lvol1
  lvol2
  lvol3
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C.5. Selection Criteria Processing Examples
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This section provides a series of examples showing how to use selection criteria in commands that process LVM logical volumes.
This example shows the initial configuration of a group of logical volumes, including thin snapshots. Thin snapshots have the "skip activation" flag set by default. This example also includes the logical volume lvol4 which also has the "skip activation" flag set. 
# lvs -o name,skip_activation,layout,role
  LV    SkipAct         Layout      Role                        
  root                  linear      public                      
  swap                  linear      public                      
  lvol1                 thin,sparse public                      
  lvol2                 thin,sparse public,origin,thinorigin    
  lvol3 skip activation thin,sparse public,snapshot,thinsnapshot
  lvol4 skip activation linear      public                      
  pool                  thin,pool   private
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The following command removes the skip activation flag from all logical volmes that are thin snapshots. 
# lvchange --setactivationskip n -S 'role=thinsnapshot'
  Logical volume "lvol3" changed.
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The following command shows the configuration of the logical volumes after executing the lvchange command. Note that the "skip activation" flag has not been unset from the logical volume that is not a thin snapshot. 
# lvs -o name,active,skip_activation,layout,role
  LV    Active SkipAct         Layout      Role                        
  root  active                 linear      public                      
  swap  active                 linear      public                      
  lvol1 active                 thin,sparse public                      
  lvol2 active                 thin,sparse public,origin,thinorigin    
  lvol3                        thin,sparse public,snapshot,thinsnapshot
  lvol4 active skip activation linear      public                      
  pool  active                 thin,pool   private
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The following command shows the configuration of the logical volumes after an additional thin origin/snapshot volume has been created. 
# lvs -o name,active,skip_activation,origin,layout,role
  LV    Active SkipAct         Origin Layout      Role                        
  root  active                        linear      public                      
  swap  active                        linear      public                      
  lvol1 active                        thin,sparse public                      
  lvol2 active                        thin,sparse public,origin,thinorigin    
  lvol3                        lvol2  thin,sparse public,snapshot,thinsnapshot
  lvol4 active skip activation        linear      public                      
  lvol5 active                        thin,sparse public,origin,thinorigin    
  lvol6                        lvol5  thin,sparse public,snapshot,thinsnapshot
  pool  active                        thin,pool   private
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The following command activates logical volumes that are both thin snapshot volumes and have an origin volume of lvol2. 
# lvchange -ay -S 'lv_role=thinsnapshot && origin=lvol2'

# lvs -o name,active,skip_activation,origin,layout,role
  LV    Active SkipAct         Origin Layout      Role                        
  root  active                        linear      public                      
  swap  active                        linear      public                      
  lvol1 active                        thin,sparse public                      
  lvol2 active                        thin,sparse public,origin,thinorigin    
  lvol3 active                 lvol2  thin,sparse public,snapshot,thinsnapshot
  lvol4 active skip activation        linear      public                      
  lvol5 active                        thin,sparse public,origin,thinorigin    
  lvol6                        lvol5  thin,sparse public,snapshot,thinsnapshot
  pool  active                        thin,pool   private
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If you execute a command on a whole item while specifying selection criteria that match an item from that whole, the entire whole item is processed. For example, if you change a volume group while selecting one or more items from that volume group, the whole volume group is selected. This example selects logical volume lvol1, which is part of volume group vg. All of the logical volumes in volume group vg are processed. 
# lvs -o name,vg_name
  LV    VG    
  root  fedora
  swap  fedora
  lvol1 vg    
  lvol2 vg    
  lvol3 vg    
  lvol4 vg    
  lvol5 vg    
  lvol6 vg    
  pool  vg 

# vgchange -ay -S 'lv_name=lvol1'
  7 logical volume(s) in volume group "vg" now active
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The following example shows a more complex selection criteria statement. In this example, all logical volumes are tagged with "mytag" if they have a role of origin and are also named lvol[456] or the logical volume size is more than 5g. 
# lvchange --addtag mytag -S '(role=origin && lv_name=~lvol[456]) || lv_size > 5g'
  Logical volume "root" changed.
  Logical volume "lvol5" changed.
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附录 D. LVM 对象标签
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An LVM tag is a word that can be used to group LVM2 objects of the same type together. Tags can be attached to objects such as physical volumes, volume groups, and logical volumes. Tags can be attached to hosts in a cluster configuration.
可在命令行的 PV、VG 或者 LV 参数中赋予标签。标签应该有 @ 作为前缀以避免混淆。每个标签都可用所有对象都拥有的标签取代来扩大范围，标签的类型根据它在命令行的位置确定。
As of the Red Hat Enterprise Linux 6.1 release, LVM tags are strings of up to 1024 characters (for earlier releases the upper length limit was 128 characters). LVM tags cannot start with a hyphen.
A valid tag can consist of a limited range of characters only. For the Red Hat Enterprise Linux 6.0 release, the allowed characters are [A-Za-z0-9_+.-]. As of the Red Hat Enterprise Linux 6.1 release, the list of allowed characters has been extended, and tags can contain the "/", "=", "!", ":", "#", and "&" characters.
Only objects in a volume group can be tagged. Physical volumes lose their tags if they are removed from a volume group; this is because tags are stored as part of the volume group metadata and that is deleted when a physical volume is removed.
以下命令列出所有带 database 标签的逻辑卷。 
lvs @database
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The following command lists the currently active host tags. 
lvm tags
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D.1. 添加和删除对象标签
复制链接

要从物理卷中添加或者删除标签，请使用 pvchange 命令的 --addtag 或者 --deltag 选项。
要从卷组中添加或者删除标签，请使用 vgchange 或 vgcreate 命令的 --addtag 或者 --deltag 选项。
要在逻辑卷中添加或者删除标签，请请使用 lvchange 或 lvcreate 命令的 --addtag 或者 --deltag 选项。
As of the Red Hat Enterprise Linux 6.1 release, you can specify multiple --addtag and --deltag arguments within a single pvchange, vgchange, or lvchange command. For example, the following command deletes the tags T9 and T10 and adds the tags T13 and T14 to the volume group grant. 
vgchange --deltag T9 --deltag T10 --addtag T13 --addtag T14 grant
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D.2. 主机标签
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In a cluster configuration, you can define host tags in the configuration files. If you set hosttags = 1 in the tags section, a host tag is automatically defined using the machine's host name. This allow you to use a common configuration file which can be replicated on all your machines so they hold identical copies of the file, but the behavior can differ between machines according to the host name.
For information on the configuration files, see 附录 B, LVM 配置文件.
对于每个主机标签，如果存在额外的配置文件 lvm_hosttag.conf，就会读取它。如果那个文件定义了新的标签，那么会在要读取的文件列表中添加进一步的配置文件。
For example, the following entry in the configuration file always defines tag1, and defines tag2 if the host name is host1. 
tags { tag1 { }  tag2 { host_list = ["host1"] } }
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D.3. 使用标签控制激活
复制链接

您可以在配置文件中指定在那个主机中只应该激活某个逻辑卷。例如：下面的条目作为激活请求的过滤器使用（比如 vgchange -ay），且只激活 vg1/lvol0 以及那些在该主机的元数据中带 database 标签的逻辑卷和卷组。 
activation { volume_list = ["vg1/lvol0", "@database" ] }
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There is a special match "@*" that causes a match only if any metadata tag matches any host tag on that machine.
另一个例子就是，考虑一下，在哪里群集中的每一台机器都在配置文件中有以下条目： 
tags { hosttags = 1 }
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如果您想要只在主机 db2 中激活 vg1/lvol2，请执行以下操作：
  1. 可从群集中的任意主机运行 lvchange --addtag @db2 vg1/lvol2。
  2. 运行 lvchange -ay vg1/lvol2。
这个解决方案包括将主机名保存在卷组元数据中。

附录 E. LVM 卷组元数据
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The configuration details of a volume group are referred to as the metadata. By default, an identical copy of the metadata is maintained in every metadata area in every physical volume within the volume group. LVM volume group metadata is stored as ASCII.
如果卷组包含很多物理卷，那么有很多元数据的冗余副本不是很有效。您可以使用 pvcreate 命令的 --metadatacopies 0 选项创建没有任何元数据副本的物理卷。一旦您选择了物理卷将包含的元数据副本的数目，您将无法修改它。选择零副本将在修改配置时提高更新速度。注意：虽然任何时候每个卷组必须至少包含一个带元数据区域的物理卷（除非您使用高级配置设置允许您在文件系统中保存卷组元数据）。如果您试图在将来分割卷组，那么每个卷组至少需要一个元数据副本。
核心元数据以 ASCII 格式保存。元数据区域是一个环形缓冲。新的元数据会附加在旧的元数据之后，然后会更新开始的指示点。
You can specify the size of metadata area with the --metadatasize. option of the pvcreate command. The default size may be too small for volume groups that contain physical volumes and logical volumes that number in the hundreds.

E.1. 物理卷标签
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默认情况下，pvcreate 命令会在第二个 512 字节部分放置物理卷标签。这个标签可选择性地放在前四个部分的任意一个中，因为扫描物理卷标签的 LVM 工具会检查前四个部分。物理卷标签以字符串 LABELONE 开始。
物理卷标签包含：
  • 物理卷 UUID
  • 以字节为单位的块设备大小
  • 数据区域位置的 NULL 终止列表
  • 元数据区域位置的 NULL 终止列表
元数据位置以偏差和大小（字节）形式保存。标签中有大约 15 个位置的空间，但 LVM 工具目前仅使用 3: 这个单数据区域以及最多两个元数据区域。

E.2. 元数据内容
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卷组元数据包含：
  • 何时以及如何创建该卷组的信息
  • 卷组信息：
卷组信息包括：
  • 名称和唯一 id
  • 无论何时更新元数据时增大的版本数目
  • 任意属性：读/写？可重新定义大小？
  • 它可能包含的所有对物理卷和逻辑卷数量的管理限制
  • 扩展大小（以扇区为单位，大小为 512 字节）
  • 一个没有排序的物理卷列表组成卷组，每个都带有：
    • 它的 UUID，用来决定包含它的块设备
    • 所有属性，比如物理卷是否可分配
    • 在物理卷中第一个扩展的开始调节（在扇区中）
    • 扩展的数目
  • 没有配需的逻辑卷列表，每个都包含
    • 排序的逻辑卷片段列表。每个片段的元数据都包括用于排序的物理卷片段或者逻辑卷片段的映射

E.3. 元数据示例
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以下显示了名为 myvg 的卷组的 LVM 卷组元数据示例。 
# Generated by LVM2: Tue Jan 30 16:28:15 2007

contents = "Text Format Volume Group"
version = 1

description = "Created *before* executing 'lvextend -L+5G /dev/myvg/mylv /dev/sdc'"

creation_host = "tng3-1"        # Linux tng3-1 2.6.18-8.el5 #1 SMP Fri Jan 26 14:15:21 EST 2007 i686
creation_time = 1170196095      # Tue Jan 30 16:28:15 2007

myvg {
        id = "0zd3UT-wbYT-lDHq-lMPs-EjoE-0o18-wL28X4"
        seqno = 3
        status = ["RESIZEABLE", "READ", "WRITE"]
        extent_size = 8192              # 4 Megabytes
        max_lv = 0
        max_pv = 0

        physical_volumes {

                pv0 {
                        id = "ZBW5qW-dXF2-0bGw-ZCad-2RlV-phwu-1c1RFt"
                        device = "/dev/sda"     # Hint only

                        status = ["ALLOCATABLE"]
                        dev_size = 35964301     # 17.1491 Gigabytes
                        pe_start = 384
                        pe_count = 4390 # 17.1484 Gigabytes
                }

                pv1 {
                        id = "ZHEZJW-MR64-D3QM-Rv7V-Hxsa-zU24-wztY19"
                        device = "/dev/sdb"     # Hint only

                        status = ["ALLOCATABLE"]
                        dev_size = 35964301     # 17.1491 Gigabytes
                        pe_start = 384
                        pe_count = 4390 # 17.1484 Gigabytes
                }

                pv2 {
                        id = "wCoG4p-55Ui-9tbp-VTEA-jO6s-RAVx-UREW0G"
                        device = "/dev/sdc"     # Hint only

                        status = ["ALLOCATABLE"]
                        dev_size = 35964301     # 17.1491 Gigabytes
                        pe_start = 384
                        pe_count = 4390 # 17.1484 Gigabytes
                }

                pv3 {
                        id = "hGlUwi-zsBg-39FF-do88-pHxY-8XA2-9WKIiA"
                        device = "/dev/sdd"     # Hint only

                        status = ["ALLOCATABLE"]
                        dev_size = 35964301     # 17.1491 Gigabytes
                        pe_start = 384
                        pe_count = 4390 # 17.1484 Gigabytes
                }
        }
        logical_volumes {

                mylv {
                        id = "GhUYSF-qVM3-rzQo-a6D2-o0aV-LQet-Ur9OF9"
                        status = ["READ", "WRITE", "VISIBLE"]
                        segment_count = 2

                        segment1 {
                                start_extent = 0
                                extent_count = 1280     # 5 Gigabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv0", 0
                                ]
                        }
                        segment2 {
                                start_extent = 1280
                                extent_count = 1280     # 5 Gigabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv1", 0
                                ]
                        }
                }
        }
}
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附录 F. 修订记录
复制链接

修订历史
修订 10.0-3Wed Mar 8 2017Steven Levine
Version for 6.9 GA Publication
修订 10.0-1Fri Dec 16 2016Steven Levine
Version for 6.9 Beta Publication
修订 9.0-5Tue Nov 29 2016Steven Levine
Updating document for 6.8.
修订 9.0-4Wed Apr 27 2016Steven Levine
Preparing document for 6.8 GA publication.
修订 9.0-3Wed Mar 9 2016Steven Levine
Initial revision for Red Hat Enterprise Linux 6.8 Beta release
修订 8.0-16Mon Jul 13 2015Steven Levine
Republish version for Red Hat Enterprise Linux 6.7
修订 8.0-14Wed Jul 8 2015Steven Levine
Initial revision for Red Hat Enterprise Linux 6.7
修订 8.0-13Tue Apr 14 2015Steven Levine
Initial revision for Red Hat Enterprise Linux 6.7 Beta release
修订 7.0-9Wed Oct 8 2014Steven Levine
Initial revision for Red Hat Enterprise Linux 6.6
修订 7.0-8Thu Aug 7 2014Steven Levine
Initial revision for Red Hat Enterprise Linux 6.6 Beta release
修订 6.0-14Wed Nov 13 2013Steven Levine
Initial revision for Red Hat Enterprise Linux 6.5
修订 6.0-10Fri Sep 27 2013Steven Levine
Initial revision for Red Hat Enterprise Linux 6.5 Beta release
修订 5.0-19Mon Feb 18 2013John Ha
Initial revision for Red Hat Enterprise Linux 6.4
修订 5.0-12Mon Nov 27 2012Steven Levine
Initial revision for Red Hat Enterprise Linux 6.4 Beta release
修订 4.0-2Fri Jun 15 2012Steven Levine
Initial revision for Red Hat Enterprise Linux 6.3
修订 3.0-1Mon Sep 19 2011Steven Levine
Initial revision for Red Hat Enterprise Linux 6.2 Beta release
修订 2.0-1Thu May 19 2011Steven Levine
Initial revision for Red Hat Enterprise Linux 6.1
修订 1.0-1Wed Nov 10 2010Steven Levine
Initial release for Red Hat Enterprise Linux 6

索引

符号

/lib/udev/rules.d directory，udev Integration with the Device Mapper
日志，日志

A

activating logical volumes
individual nodes，在群集的独立节点中激活逻辑卷
activating volume groups，激活和失活卷组
individual nodes，激活和失活卷组
local node only，激活和失活卷组
administrative procedures，LVM 管理总览
allocation，LVM Allocation
policy，创建卷组
preventing，防止在物理卷中进行分配
archive file，逻辑卷备份，备份卷组元数据

B

backup
file，逻辑卷备份
metadata，逻辑卷备份，备份卷组元数据
backup file，备份卷组元数据
block device
scanning，扫描块设备

C

cache file
building，为卷组扫描磁盘来建立缓存文件
cache logical volume
creation，Creating LVM Cache Logical Volumes
cache volumes，Cache Volumes
cluster environment，群集逻辑卷管理器（CLVM），在群集中创建 LVM 卷
CLVM
definition，群集逻辑卷管理器（CLVM）
clvmd daemon，群集逻辑卷管理器（CLVM）
command line units，使用 CLI 命令
configuration examples，LVM 配置示例
creating
logical volume，Creating Linear Logical Volumes
logical volume, example，在三个磁盘中创建 LVM 逻辑卷
LVM volumes in a cluster，在群集中创建 LVM 卷
physical volumes，创建物理卷
striped logical volume, example，创建条状逻辑卷
volume group, clustered，在群集中创建卷组
volume groups，创建卷组
creating LVM volumes
overview，创建逻辑卷总览

D

data relocation, online，在线数据重定位
deactivating volume groups，激活和失活卷组
exclusive on one node，激活和失活卷组
local node only，激活和失活卷组
device numbers
major，持久的设备号码
minor，持久的设备号码
persistent，持久的设备号码
device path names，使用 CLI 命令
device scan filters，用过滤器控制 LVM 设备扫描
device size, maximum，创建卷组
device special file directory，创建卷组
display
sorting output，LVM 报告排序
displaying
logical volumes，显示逻辑卷，lvs 命令
physical volumes，显示物理卷，pvs 命令
volume groups，显示卷组，vgs 命令

E

extent
allocation，创建卷组，LVM Allocation
definition，卷组，创建卷组

F

failed devices
displaying，在失败的设备中显示信息。
features, new and changed，New and Changed Features
feedback
contact information for this manual，We Need Feedback!
file system
growing on a logical volume，在逻辑卷中增大文件系统
filters，用过滤器控制 LVM 设备扫描

G

growing file system
logical volume，在逻辑卷中增大文件系统

H

help display，使用 CLI 命令

I

initializing
partitions，初始化物理卷
physical volumes，初始化物理卷
Insufficient Free Extents message，逻辑卷没有足够的可用扩展

L

linear logical volume
converting to mirrored，修改镜像卷配置
creation，Creating Linear Logical Volumes
definition，线性卷
logical volume
activation，Controlling Logical Volume Activation
administration, general，逻辑卷管理
cache，Creating LVM Cache Logical Volumes
changing parameters，修改逻辑卷组的参数
creation，Creating Linear Logical Volumes
creation example，在三个磁盘中创建 LVM 逻辑卷
definition，逻辑卷，LVM 逻辑卷
displaying，显示逻辑卷，为 LVM 自定义报告，lvs 命令
exclusive access，在群集的独立节点中激活逻辑卷
extending，增大逻辑卷
growing，增大逻辑卷
linear，Creating Linear Logical Volumes
local access，在群集的独立节点中激活逻辑卷
lvs display arguments，lvs 命令
mirrored，创建镜像卷
reducing，缩小逻辑卷
removing，删除逻辑卷
renaming，重新命名逻辑卷
shrinking，缩小逻辑卷
snapshot，创建快照卷
striped，创建条状卷
thinly-provisioned，Creating Thinly-Provisioned Logical Volumes
thinly-provisioned snapshot，Creating Thinly-Provisioned Snapshot Volumes
lvchange command，修改逻辑卷组的参数
lvconvert command，修改镜像卷配置
lvcreate command，Creating Linear Logical Volumes
lvdisplay command，显示逻辑卷
lvextend command，增大逻辑卷
LVM
architecture overview，LVM 构架总览
clustered，群集逻辑卷管理器（CLVM）
components，LVM 构架总览，LVM 组成
custom report format，为 LVM 自定义报告
directory structure，创建卷组
help，使用 CLI 命令
history，LVM 构架总览
label，物理卷
logging，日志
logical volume administration，逻辑卷管理
physical volume administration，物理卷管理
physical volume, definition，物理卷
volume group, definition，卷组
LVM1，LVM 构架总览
LVM2，LVM 构架总览
lvmdiskscan command，扫描块设备
lvmetad daemon，The Metadata Daemon (lvmetad)
lvreduce command，缩小逻辑卷
lvremove command，删除逻辑卷
lvrename command，重新命名逻辑卷
lvs command，为 LVM 自定义报告，lvs 命令
display arguments，lvs 命令
lvscan command，显示逻辑卷

M

man page display，使用 CLI 命令
metadata
backup，逻辑卷备份，备份卷组元数据
recovery，修复物理卷元数据
metadata daemon，The Metadata Daemon (lvmetad)
mirrored logical volume
clustered，Creating a Mirrored LVM Logical Volume in a Cluster
converting to linear，修改镜像卷配置
creation，创建镜像卷
definition，镜像逻辑卷
extending，Extending a Mirrored Volume
failure policy，Mirrored Logical Volume Failure Policy
failure recovery，修复 LVM 镜像错误
growing，Extending a Mirrored Volume
reconfiguration，修改镜像卷配置
mirror_image_fault_policy configuration parameter，Mirrored Logical Volume Failure Policy
mirror_log_fault_policy configuration parameter，Mirrored Logical Volume Failure Policy

O

online data relocation，在线数据重定位
overview
features, new and changed，New and Changed Features

P

partition type, setting，设定分区类型
partitions
multiple，一个磁盘中有多个分区
path names，使用 CLI 命令
persistent device numbers，持久的设备号码
physical extent
preventing allocation，防止在物理卷中进行分配
physical volume
adding to a volume group，在卷组中添加物理卷
administration, general，物理卷管理
creating，创建物理卷
definition，物理卷
display，pvs 命令
displaying，显示物理卷，为 LVM 自定义报告
illustration，LVM Physical Volume Layout
initializing，初始化物理卷
layout，LVM Physical Volume Layout
pvs display arguments，pvs 命令
recovery，替换丢失的物理卷
removing，删除物理卷
removing from volume group，从卷组中删除物理卷
removing lost volume，从卷组中删除丢失的物理卷。
resizing，重新设置物理卷大小
pvdisplay command，显示物理卷
pvmove command，在线数据重定位
pvremove command，删除物理卷
pvresize command，重新设置物理卷大小
pvs command，为 LVM 自定义报告
display arguments，pvs 命令
pvscan command，显示物理卷

R

RAID logical volume，RAID Logical Volumes
removing
disk from a logical volume，从逻辑卷中删除磁盘
logical volume，删除逻辑卷
physical volumes，删除物理卷
renaming
logical volume，重新命名逻辑卷
volume group，重命名卷组
report format, LVM devices，为 LVM 自定义报告
resizing
physical volume，重新设置物理卷大小
rules.d directory，udev Integration with the Device Mapper

S

scanning
block devices，扫描块设备
scanning devices, filters，用过滤器控制 LVM 设备扫描
snapshot logical volume
creation，创建快照卷
snapshot volume
definition，快照卷
striped logical volume
creation，创建条状卷
creation example，创建条状逻辑卷
definition，条状逻辑卷
extending，扩展条状卷
growing，扩展条状卷

T

thin snapshot volume，Thinly-Provisioned Snapshot Volumes
thin volume
creation，Creating Thinly-Provisioned Logical Volumes
thinly-provisioned logical volume，Thinly-Provisioned Logical Volumes (Thin Volumes)
creation，Creating Thinly-Provisioned Logical Volumes
thinly-provisioned snapshot logical volume
creation，Creating Thinly-Provisioned Snapshot Volumes
thinly-provisioned snapshot volume，Thinly-Provisioned Snapshot Volumes
troubleshooting，LVM 故障排除

U

udev device manager，Device Mapper Support for the udev Device Manager
udev rules，udev Integration with the Device Mapper
units, command line，使用 CLI 命令

V

verbose output，使用 CLI 命令
vgcfbackup command，备份卷组元数据
vgcfrestore command，备份卷组元数据
vgchange command，修改卷组参数
vgcreate command，创建卷组，在群集中创建卷组
vgdisplay command，显示卷组
vgexport command，将卷组移动到其它系统中
vgextend command，在卷组中添加物理卷
vgimport command，将卷组移动到其它系统中
vgmerge command，合并卷组
vgmknodes command，重新创建卷组目录
vgreduce command，从卷组中删除物理卷
vgrename command，重命名卷组
vgs command，为 LVM 自定义报告
display arguments，vgs 命令
vgscan command，为卷组扫描磁盘来建立缓存文件
vgsplit command，分割卷组
volume group
activating，激活和失活卷组
administration, general，卷组管理
changing parameters，修改卷组参数
combining，合并卷组
creating，创建卷组
creating in a cluster，在群集中创建卷组
deactivating，激活和失活卷组
definition，卷组
displaying，显示卷组，为 LVM 自定义报告，vgs 命令
extending，在卷组中添加物理卷
growing，在卷组中添加物理卷
merging，合并卷组
moving between systems，将卷组移动到其它系统中
reducing，从卷组中删除物理卷
removing，删除卷组
renaming，重命名卷组
shrinking，从卷组中删除物理卷
splitting，分割卷组
example procedure，分割卷组
vgs display arguments，vgs 命令

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