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Chapter 68. Configuring and managing logical volumes

68.1. Overview of logical volume management

Logical volume management (LVM) creates a layer of abstraction over physical storage, which helps you to create logical storage volumes. This provides much greater flexibility in a number of ways than using physical storage directly.

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.

68.1.1. LVM architecture

The following are the components of LVM:

Physical volume: A physical volume (PV) is a partition or whole disk designated for LVM use. For more information, see Managing LVM physical volumes.
Volume group: A volume group (VG) is a collection of physical volumes (PVs), which creates a pool of disk space out of which logical volumes can be allocated. For more information, see Managing LVM volume groups.
Logical volume: A logical volume represents a mountable storage device. For more information, see Managing LVM logical volumes.

The following diagram illustrates the components of LVM:

Figure 68.1. LVM logical volume components

68.1.2. Advantages of LVM

Logical volumes provide the following advantages over using physical storage directly:

Flexible capacity: When using logical volumes, you can aggregate devices and partitions into a single logical volume. With this functionality, file systems can extend across multiple devices as though they were a single, large one.
Resizeable storage volumes: You can extend logical volumes or reduce logical volumes in size with simple software commands, without reformatting and repartitioning the underlying devices.
Online data relocation: To deploy newer, faster, or more resilient storage subsystems, you can move data while your system is active. Data can be rearranged on disks while the disks are in use. For example, you can empty a hot-swappable disk before removing it.
Convenient device naming: Logical storage volumes can be managed with user-defined and custom names.
Striped Volumes: You can create a logical volume that stripes data across two or more devices. This can dramatically increase throughput.
RAID volumes: Logical volumes provide a convenient way to configure RAID for your data. This provides protection against device failure and improves performance.
Volume snapshots: You can take snapshots, which is a point-in-time copy of logical volumes for consistent backups or to test the effect of changes without affecting the real data.
Thin volumes: Logical volumes can be thinly provisioned. This allows you to create logical volumes that are larger than the available physical space.
Cache volumes: A cache logical volume uses a fast block device, such as an SSD drive to improve the performance of a larger and slower block device.

68.2. Managing LVM physical volumes

The physical volume (PV) is a partition or whole disk designated for LVM use. To use the device for an LVM logical volume, the device must be initialized as a physical volume.

If you are using a whole disk device for your physical volume, the disk must have no partition table. For DOS disk partitions, the partition id should be set to 0x8e using the fdisk or cfdisk command or an equivalent. If you are using a whole disk device for your physical volume, the disk must have no partition table. Any existing partition table must be erased, which will effectively destroy all data on that disk. You can remove an existing partition table using the wipefs -a <PhysicalVolume>` command as root.

68.2.1. Overview of physical volumes

Initializing a block device as a physical volume places a label near the start of the device. The following describes the LVM label:

An LVM label provides correct identification and device ordering for a physical device. An unlabeled, non-LVM device can change names across reboots depending on the order they are discovered by the system during boot. An LVM label remains persistent across reboots and throughout a cluster.
The LVM label identifies the device as an LVM physical volume. It contains a random unique identifier, the UUID for the physical volume. It also stores the size of the block device in bytes, and it records where the LVM metadata will be stored on the device.
By default, the LVM label is placed in the second 512-byte sector. You can overwrite this default setting by placing the label on any of the first 4 sectors when you create the physical volume. This allows LVM volumes to co-exist with other users of these sectors, if necessary.

The following describes the LVM metadata:

The LVM metadata contains the configuration details of the LVM volume groups on your system. By default, an identical copy of the metadata is maintained in every metadata area in every physical volume within the volume group. LVM metadata is small and stored as ASCII.
Currently LVM allows you to store 0, 1, or 2 identical copies of its metadata on each physical volume. The default is 1 copy. Once you configure the number of metadata copies on the physical volume, you cannot change that number at a later time. The first copy is stored at the start of the device, shortly after the label. If there is a second copy, it is placed at the end of the device. If you accidentally overwrite the area at the beginning of your disk by writing to a different disk than you intend, a second copy of the metadata at the end of the device will allow you to recover the metadata.

The following diagram illustrates 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.

Note

In the Linux kernel and throughout this document, sectors are considered to be 512 bytes in size.

Figure 68.2. Physical volume layout

Additional resources

Multiple partitions on a disk

68.2.2. Multiple partitions on a disk

You can create physical volumes (PV) out of disk partitions by using LVM.

Red Hat recommends that you create a single partition that covers the whole disk to label as an LVM physical volume for the following reasons:

Administrative convenience: It is easier to keep track of the hardware in a system if each real disk only appears once. This becomes particularly true if a disk fails.
Striping performance: 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.
RAID redundancy: LVM cannot determine that the two physical volumes are on the same device. If you create a RAID logical volume when two physical volumes are on the same device, performance and fault tolerance could be lost.

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 volumes.

Note that although LVM supports using a non-partitioned disk as physical volume, it is recommended to create a single, whole-disk partition because creating a PV without a partition can be problematic in a mixed operating system environment. Other operating systems may interpret the device as free, and overwrite the PV label at the beginning of the drive.

68.2.3. Creating LVM physical volume

This procedure describes how to create and label LVM physical volumes (PVs).

In this procedure, replace the /dev/vdb1, /dev/vdb2, and /dev/vdb3 with the available storage devices in your system.

Prerequisites

The lvm2 package is installed.

Procedure

Create multiple physical volumes by using the space-delimited device names as arguments to the pvcreate command:
```
# pvcreate /dev/vdb1 /dev/vdb2 /dev/vdb3
  Physical volume "/dev/vdb1" successfully created.
  Physical volume "/dev/vdb2" successfully created.
  Physical volume "/dev/vdb3" successfully created.
```
This places a label on /dev/vdb1, /dev/vdb2, and /dev/vdb3, marking them as physical volumes belonging to LVM.

View the created physical volumes by using any one of the following commands as per your requirement:

The pvdisplay command, which provides a verbose multi-line output for each physical volume. It displays physical properties, such as size, extents, volume group, and other options in a fixed format:

# pvdisplay
--- NEW Physical volume ---
  PV Name               /dev/vdb1
  VG Name
  PV Size               1.00 GiB
[..]
--- NEW Physical volume ---
  PV Name               /dev/vdb2
  VG Name
  PV Size               1.00 GiB
[..]
--- NEW Physical volume ---
  PV Name               /dev/vdb3
  VG Name
  PV Size               1.00 GiB
[..]

The pvs command provides physical volume information in a configurable form, displaying one line per physical volume:

# pvs
  PV         VG  Fmt    Attr    PSize      PFree
/dev/vdb1        lvm2           1020.00m   0
/dev/vdb2        lvm2           1020.00m   0
/dev/vdb3        lvm2           1020.00m   0

The pvscan command scans all supported LVM block devices in the system for physical volumes. You can define a filter in the lvm.conf file so that this command avoids scanning specific physical volumes:

# pvscan
  PV  /dev/vdb1                      lvm2 [1.00 GiB]
  PV  /dev/vdb2                      lvm2 [1.00 GiB]
  PV  /dev/vdb3                      lvm2 [1.00 GiB]

Additional resources

pvcreate(8), pvdisplay(8), pvs(8), pvscan(8), and lvm(8) man pages

68.2.4. Removing LVM physical volumes

If a device is no longer required for use by LVM, you can remove the LVM label by using the pvremove command. Executing the pvremove command zeroes the LVM metadata on an empty physical volume.

Procedure

Remove a physical volume:

# pvremove /dev/vdb3
Labels on physical volume "/dev/vdb3" successfully wiped.

View the existing physical volumes and verify if the required volume is removed:

# pvs
  PV         VG   Fmt    Attr    PSize      PFree
/dev/vdb1  	    lvm2           1020.00m   0
/dev/vdb2  	    lvm2           1020.00m   0

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. For more information, see Removing physical volumes from a volume group

Additional resources

pvremove(8) man page

68.2.5. Additional resources

Creating a partition table on a disk with parted.
parted(8) man page.

68.3. Managing LVM volume groups

A volume group (VG) is a collection of physical volumes (PVs), which creates a pool of disk space out of which logical volumes (LVs) can be allocated.

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.

A logical volume is allocated into logical extents of the same size as the physical extents. The extent size is therefore the same for all logical volumes in the volume group. The volume group maps the logical extents to physical extents.

68.3.1. Creating LVM volume group

This procedure describes how to create an LVM volume group (VG) myvg, by using the /dev/vdb1 and /dev/vdb2 physical volumes.

Prerequisites

The lvm2 package is installed.
One or more physical volumes are created. For more information about creating physical volumes, see Creating LVM physical volume.

Procedure

Create a volume group:
```
# vgcreate myvg /dev/vdb1 /dev/vdb2
 Volume group "myvg" successfully created.
```
This creates a VG with the name of myvg. The PVs /dev/vdb1 and /dev/vdb2 are the base storage level for the myvg VG .
View the created volume groups by using any one of the following commands according to your requirement:
1. The vgs command provides volume group information in a configurable form, displaying one line per volume groups:
```
# vgs
  VG    #PV #LV #SN  Attr  VSize   VFree
 myvg   2    0   0   wz-n  159.99g 159.99g
```
2. The vgdisplay command displays volume group properties such as size, extents, number of physical volumes, and other options in a fixed form. The following example shows the output of the vgdisplay command for the volume group myvg. To display all existing volume groups, do not specify a volume group:
```
# vgdisplay myvg
  --- Volume group ---
  VG Name               myvg
  System ID
  Format                lvm2
  Metadata Areas        4
  Metadata Sequence No  6
  VG Access             read/write
[..]
```
3. The vgscan command scans all supported LVM block devices in the system for volume group:
```
# vgscan
  Found volume group "myvg" using metadata type lvm2
```

Optional: Increase a volume group’s capacity by adding one or more free physical volumes:

# vgextend myvg /dev/vdb3
Physical volume "/dev/vdb3" successfully created.
Volume group "myvg" successfully extended

Optional: Rename an existing volume group:

# vgrename myvg myvg1
Volume group "myvg" successfully renamed to "myvg1"

Additional resources

vgcreate(8), vgextend(8), vgdisplay(8), vgs(8), vgscan(8), vgrename(8), and lvm(8) man pages

68.3.2. Combining LVM volume groups

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.

Procedure

Merge the inactive volume group databases into the active or inactive volume group myvg giving verbose runtime information:
```
# vgmerge -v myvg databases
```

Additional resources

vgmerge(8) man page

68.3.3. Removing physical volumes from a volume group

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.

Procedure

If the physical volume is still being used, migrate the data to another physical volume from the same volume group :

# pvmove /dev/vdb3
  /dev/vdb3: Moved: 2.0%
 ...
  /dev/vdb3: Moved: 79.2%
 ...
  /dev/vdb3: Moved: 100.0%

If there are no enough free extents on the other physical volumes in the existing volume group:

Create a new physical volume from /dev/vdb4:

# pvcreate /dev/vdb4
  Physical volume "/dev/vdb4" successfully created

Add the newly created physical volume to the myvg volume group:

# vgextend myvg /dev/vdb4
  Volume group "myvg" successfully extended

Move the data from /dev/vdb3 to /dev/vdb4:

# pvmove /dev/vdb3 /dev/vdb4
  /dev/vdb3: Moved: 33.33%
  /dev/vdb3: Moved: 100.00%

Remove the physical volume /dev/vdb3 from the volume group:

# vgreduce myvg /dev/vdb3
Removed "/dev/vdb3" from volume group "myvg"

Verification

Verify if the /dev/vdb3 physical volume is removed from the myvg volume group:

# pvs
  PV           VG    Fmt   Attr   PSize        PFree      Used
  /dev/vdb1 myvg  lvm2   a--    1020.00m    0          1020.00m
  /dev/vdb2 myvg  lvm2   a--    1020.00m    0          1020.00m
  /dev/vdb3   	    lvm2   a--    1020.00m   1008.00m    12.00m

Additional resources

vgreduce(8), pvmove(8), and pvs(8) man pages

68.3.4. Splitting a LVM volume group

This procedure describes how to split the existing volume group. If there is enough unused space on the physical volumes, a new volume group can be created without adding new disks.

In the initial setup, the volume group myvg consists of /dev/vdb1, /dev/vdb2, and /dev/vdb3. After completing this procedure, the volume group myvg will consist of /dev/vdb1 and /dev/vdb2, and the second volume group, yourvg, will consist of /dev/vdb3.

Prerequisites

You have sufficient space in the volume group. Use the vgscan command to determine how much free space is currently available in the volume group.
Depending on the free capacity in the existing physical volume, move all the used physical extents to other physical volume using the pvmove command. For more information, see Removing physical volumes from a volume group.

Procedure

Split the existing volume group myvg to the new volume group yourvg:
```
# vgsplit myvg yourvg /dev/vdb3
  Volume group "yourvg" successfully split from "myvg"
```
Note
If you have created a logical volume using the existing volume group, use the following command to deactivate the logical volume:
```
# lvchange -a n /dev/myvg/mylv
```
For more information on creating logical volumes, see Managing LVM logical volumes.

View the attributes of the two volume group:

# 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

Verification

Verify if the newly created volume group yourvg consists of /dev/vdb3 physical volume:

# pvs
  PV           VG      Fmt   Attr   PSize        PFree      Used
  /dev/vdb1 myvg   lvm2   a--    1020.00m    0          1020.00m
  /dev/vdb2 myvg   lvm2   a--    1020.00m    0          1020.00m
  /dev/vdb3 yourvg lvm2   a--    1020.00m   1008.00m    12.00m

Additional resources

vgsplit(8), vgs(8), and pvs(8) man pages

68.3.5. Moving a volume group to another system

You can move an entire LVM volume group to another system. It is recommended that you use the vgexport and vgimport commands when you do this.

Note

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.

The vgexport command makes an inactive volume group inaccessible to the system, which allows you to detach its physical volumes. The vgimport command makes a volume group accessible to a machine again after the vgexport command has made it inactive.

To move a volume group from one system to another, perform the following steps:

Make sure that no users are accessing files on the active volumes in the volume group, then unmount the logical volumes.
Use the -a n argument of the vgchange command to mark the volume group as inactive, which prevents any further activity on the volume group.
Use the vgexport command to export the volume group. This prevents it from being accessed by the system from which you are removing it.
After you export the volume group, the physical volume will show up as being in an exported volume group when you execute the pvscan command, as in the following example.
```
# 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]
  ...
```
When the system is next shut down, you can unplug the disks that constitute the volume group and connect them to the new system.
When the disks are plugged into the new system, use the vgimport command to import the volume group, making it accessible to the new system.
Activate the volume group with the -a y argument of the vgchange command.
Mount the file system to make it available for use.

68.3.6. Removing LVM volume groups

This procedure describes how to remove an existing volume group.

Prerequisites

The volume group contains no logical volumes. To remove logical volumes from a volume group, see Removing LVM logical volumes.

Procedure

If the volume group exists in a clustered environment, stop the lockspace of the volume group on all other nodes. Use the following command on all nodes except the node where you are performing the removing:
```
# vgchange --lockstop vg-name
```
Wait for the lock to stop.

Remove the volume group:

# vgremove vg-name
  Volume group "vg-name" successfully removed

Additional resources

vgremove(8) man page

68.4. Managing LVM logical volumes

A logical volume is a virtual, block storage device that a file system, database, or application can use. To create an LVM logical volume, the physical volumes (PVs) are combined into a volume group (VG). This creates a pool of disk space out of which LVM logical volumes (LVs) can be allocated.

68.4.1. Overview of logical volumes

An administrator can grow or shrink logical volumes without destroying data, unlike standard disk partitions. If the physical volumes in a volume group are on separate drives or RAID arrays, then administrators can also spread a logical volume across the storage devices.

You can lose data if you shrink a logical volume to a smaller capacity than the data on the volume requires. Further, some file systems are not capable of shrinking. To ensure maximum flexibility, create logical volumes to meet your current needs, and leave excess storage capacity unallocated. You can safely extend logical volumes to use unallocated space, depending on your needs.

Important

On AMD, Intel, ARM systems, and IBM Power Systems servers, the boot loader cannot read LVM volumes. You must make a standard, non-LVM disk partition for your /boot partition. On IBM Z, the zipl boot loader supports /boot on LVM logical volumes with linear mapping. By default, the installation process always creates the / and swap partitions within LVM volumes, with a separate /boot partition on a physical volume.

The following are the different types of logical volumes:

Linear volumes

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.

Striped logical volumes

When you write data to an LVM logical volume, the file system lays the data out across the underlying physical volumes. You can control the way the data is written to the physical volumes by creating a striped logical volume. For large sequential reads and writes, this can improve the efficiency of the data I/O.

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.

RAID logical volumes

LVM supports RAID levels 0, 1, 4, 5, 6, and 10. RAID logical volumes are not cluster-aware. 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.

Thin-provisioned logical volumes (thin volumes)

Using thin-provisioned logical volumes, you can create logical volumes that are larger than the available physical storage. Creating a thinly provisioned set of volumes allows the system to allocate what you use instead of allocating the full amount of storage that is requested

Snapshot volumes

The LVM snapshot feature provides the ability to create virtual images of a device at a particular instant without causing a service interruption. When a change is made to the original device (the origin) after a snapshot is taken, the snapshot feature makes a copy of the changed data area as it was prior to the change so that it can reconstruct the state of the device.

Thin-provisioned snapshot volumes

Using thin-provisioned snapshot volumes, you can have more virtual devices to be stored on the same data volume. Thinly provisioned snapshots are useful because you are not copying all of the data that you are looking to capture at a given time.

Cache volumes

LVM supports the use of fast block devices, such as SSD drives as write-back or write-through 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.

68.4.2. Using CLI commands

The following sections describe some general operational features of LVM CLI commands.

Specifying units in a command line argument

When sizes are required in a command line argument, units can always be specified explicitly. If you do not specify a unit, then a default is assumed, usually KB or MB. LVM CLI commands do not accept fractions.

When specifying units in a command line argument, LVM is case-insensitive; specifying M or m is equivalent, for example, and powers of 2 (multiples of 1024) are used. However, when specifying the --units argument in a command, lower-case indicates that units are in multiples of 1024 while upper-case indicates that units are in multiples of 1000.

Specifying volume groups and logical volumes

Note the following when specifying volume groups or logical volumes in an LVM CLI command.

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.

Increasing output verbosity

All LVM commands accept a -v argument, which can be entered multiple times to increase the output verbosity. The following examples shows the default output of the lvcreate command.

# lvcreate -L 50MB new_vg
  Rounding up size to full physical extent 52.00 MB
  Logical volume "lvol0" created

The following command shows the output of the lvcreate command with the -v argument.

# lvcreate -v -L 50MB new_vg
  Rounding up size to full physical extent 52.00 MB
    Archiving volume group "new_vg" metadata (seqno 1).
    Creating logical volume lvol0
    Creating volume group backup "/etc/lvm/backup/new_vg" (seqno 2).
    Activating logical volume new_vg/lvol0.
    activation/volume_list configuration setting not defined: Checking only host tags for new_vg/lvol0.
    Creating new_vg-lvol0
    Loading table for new_vg-lvol0 (253:0).
    Resuming new_vg-lvol0 (253:0).
    Wiping known signatures on logical volume "new_vg/lvol0"
    Initializing 4.00 KiB of logical volume "new_vg/lvol0" with value 0.
  Logical volume "lvol0" created

The -vv, -vvv and the -vvvv arguments display increasingly more details about the command execution. The -vvvv argument provides the maximum amount of information at this time. The following example shows the first few lines of output for the lvcreate command with the -vvvv argument specified.

# 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
...

Displaying help for LVM CLI commands

You can display help for any of the LVM CLI commands with the --help argument of the command.

# commandname --help

To display the man page for a command, execute the man command:

# man commandname

The man lvm command provides general online information about LVM.

68.4.3. Creating LVM logical volume

This procedure describes how to create mylv LVM logical volume (LV) from the myvg volume group, which is created by using the /dev/vdb1, /dev/vdb2, and /dev/vdb3 physical volumes.

Prerequisites

The lvm2 package is installed.
The volume group is created. For more information, see Creating LVM volume group.

Procedure

Create a logical volume:
```
# lvcreate -n mylv -L 500M myvg
```
Use the -n option to set the LV name to mylv, and the -L option to set the size of LV in units of Mb, but it is possible to use any other units. The LV type is linear by default, but the user can specify the desired type by using the --type option.
Important
The command fails if the VG does not have a sufficient number of free physical extents for the requested size and type.

View the created logical volumes by using any one of the following commands as per your requirement:

The lvs command provides logical volume information in a configurable form, displaying one line per logical volume:

# lvs
  LV   VG   Attr         LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
 mylv myvg -wi-ao----   500.00m

The lvdisplay command displays logical volume properties, such as size, layout, and mapping in a fixed format:

# lvdisplay -v /dev/myvg/mylv
  --- Logical volume ---
  LV Path                /dev/myvg/mylv
  LV Name                mylv
  VG Name                myvg
  LV UUID                YTnAk6-kMlT-c4pG-HBFZ-Bx7t-ePMk-7YjhaM
  LV Write Access        read/write
[..]

The lvscan command scans for all logical volumes in the system and lists them:
```
# lvscan
 ACTIVE                   '/dev/myvg/mylv' [500.00 MiB] inherit
```

Create a file system on the logical volume. The following command creates an xfs file system on the logical volume:

# mkfs.xfs /dev/myvg/mylv
meta-data=/dev/myvg/mylv       isize=512    agcount=4, agsize=32000 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1
data     =                       bsize=4096   blocks=128000, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=1368, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
Discarding blocks...Done.

Mount the logical volume and report the file system disk space usage:

# mount /dev/myvg/mylv /mnt

# df -h
Filesystem               1K-blocks  Used   Available Use% Mounted on

/dev/mapper/myvg-mylv   506528    29388  477140     6%   /mnt

Additional resources

lvcreate(8), lvdisplay(8), lvs(8), lvscan(8), lvm(8) and mkfs.xfs(8) man pages

68.4.4. Creating a RAID0 striped logical volume

A RAID0 logical volume spreads logical volume data across multiple data subvolumes in units of stripe size. The following procedure creates an LVM RAID0 logical volume called mylv that stripes data across the disks.

Prerequisites

You have created three or more physical volumes. For more information on creating physical volumes, see Creating LVM physical volume.
You have created the volume group. For more information, see Creating LVM volume group.

Procedure

Create a RAID0 logical volume from the existing volume group. The following command creates the RAID0 volume mylv from the volume group myvg, which is 2G in size, with three stripes and a stripe size of 4kB:

# lvcreate --type raid0 -L 2G --stripes 3 --stripesize 4 -n mylv my_vg
  Rounding size 2.00 GiB (512 extents) up to stripe boundary size 2.00 GiB(513 extents).
  Logical volume "mylv" created.

Create a file system on the RAID0 logical volume. The following command creates an ext4 file system on the logical volume:
```
# mkfs.ext4 /dev/my_vg/mylv
```

Mount the logical volume and report the file system disk space usage:

# mount /dev/my_vg/mylv /mnt

# df
Filesystem             1K-blocks     Used  Available  Use% Mounted on
/dev/mapper/my_vg-mylv   2002684     6168  1875072    1%   /mnt

Verification

View the created RAID0 stripped logical volume:

# lvs -a -o +devices,segtype my_vg
  LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert Devices Type
  mylv my_vg rwi-a-r--- 2.00g mylv_rimage_0(0),mylv_rimage_1(0),mylv_rimage_2(0) raid0
  [mylv_rimage_0] my_vg iwi-aor--- 684.00m /dev/sdf1(0) linear
  [mylv_rimage_1] my_vg iwi-aor--- 684.00m /dev/sdg1(0) linear
  [mylv_rimage_2] my_vg iwi-aor--- 684.00m /dev/sdh1(0) linear

68.4.5. Renaming LVM logical volumes

This procedure describes how to rename an existing logical volume mylv to mylv1.

Procedure

If the logical volume is currently mounted, unmount the volume:
```
# umount /mnt
```
Replace /mnt with the mount point.

Rename an existing logical volume:

# lvrename myvg mylv mylv1
Renamed "mylv" to "mylv1" in volume group "myvg"

You can also rename the logical volume by specifying the full paths to the devices:

# lvrename /dev/myvg/mylv /dev/myvg/mylv1

Additional resources

lvrename(8) man page

68.4.6. Removing a disk from a logical volume

This procedure describes how to remove a disk from an existing logical volume, either to replace the disk or to use the disk as part of a different volume.

In order to remove a disk, you must first move the extents on the LVM physical volume to a different disk or set of disks.

Procedure

View the used and free space of physical volumes when using the LV:

# pvs -o+pv_used
  PV          VG    Fmt    Attr   PSize      PFree     Used
 /dev/vdb1 myvg  lvm2   a--    1020.00m    0         1020.00m
 /dev/vdb2 myvg  lvm2   a--    1020.00m    0         1020.00m
 /dev/vdb3 myvg  lvm2   a--    1020.00m   1008.00m   12.00m

Move the data to other physical volume:
1. If there are enough free extents on the other physical volumes in the existing volume group, use the following command to move the data:
```
# pvmove /dev/vdb3
  /dev/vdb3: Moved: 2.0%
 ...
  /dev/vdb3: Moved: 79.2%
 ...
  /dev/vdb3: Moved: 100.0%
```
2. If there are no enough free extents on the other physical volumes in the existing volume group, use the following commands to add a new physical volume, extend the volume group using the newly created physical volume, and move the data to this physical volume:
```
# pvcreate /dev/vdb4
  Physical volume "/dev/vdb4" successfully created

# vgextend myvg /dev/vdb4
  Volume group "myvg" successfully extended

# pvmove /dev/vdb3 /dev/vdb4
  /dev/vdb3: Moved: 33.33%
  /dev/vdb3: Moved: 100.00%
```
Remove the physical volume:
```
# vgreduce myvg /dev/vdb3
Removed "/dev/vdb3" from volume group "myvg"
```
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:
```
# vgreduce --removemissing myvg
```

Additional resources

pvmove(8), vgextend(8), vereduce(8), and pvs(8) man pages

68.4.7. Removing LVM logical volumes

This procedure describes how to remove an existing logical volume /dev/myvg/mylv1 from the volume group myvg.

Procedure

If the logical volume is currently mounted, unmount the volume:
```
# umount /mnt
```
If the logical volume exists in a clustered environment, deactivate the logical volume on all nodes where it is active. Use the following command on each such node:
```
# lvchange --activate n vg-name/lv-name
```
Remove the logical volume using the lvremove utility:
```
# lvremove /dev/myvg/mylv1

Do you really want to remove active logical volume "mylv1"? [y/n]: y
Logical volume "mylv1" successfully removed
```
Note
In this case, the logical volume has not been deactivated. If you explicitly deactivated the logical volume before removing it, you would not see the prompt verifying whether you want to remove an active logical volume.

Additional resources

lvremove(8) man page

68.4.8. Configuring persistent device numbers

Major and minor device numbers are allocated dynamically at module load. Some applications work best if the block device is always activated with the same device (major and minor) number. You can specify these with the lvcreate and the lvchange commands by using the following arguments:

--persistent y --major major --minor minor

Use a large minor number to be sure that it has not already been allocated to another device dynamically.

If you are exporting a file system using NFS, specifying the fsid parameter in the exports file may avoid the need to set a persistent device number within LVM.

68.4.9. Specifying LVM extent size

When physical volumes are used to create a volume group, its disk space is divided into 4MB extents, by default. This extent is the minimum amount by which the logical volume may be increased or decreased in size. Large numbers of extents will have no impact on I/O performance of the logical volume.

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.

68.4.10. Managing LVM logical volumes using RHEL System Roles

Use the storage role to perform the following tasks:

Create an LVM logical volume in a volume group consisting of multiple disks.
Create an ext4 file system with a given label on the logical volume.
Persistently mount the ext4 file system.

Prerequisites

An Ansible playbook including the storage role

68.4.10.1. Example Ansible playbook to manage logical volumes

This section provides an example Ansible playbook. This playbook applies the storage role to create an LVM logical volume in a volume group.

Example 68.1. A playbook that creates a mylv logical volume in the myvg volume group

- hosts: all
  vars:
    storage_pools:
      - name: myvg
        disks:
          - sda
          - sdb
          - sdc
        volumes:
          - name: mylv
            size: 2G
            fs_type: ext4
            mount_point: /mnt/data
  roles:
    - rhel-system-roles.storage

The myvg volume group consists of the following disks:
- /dev/sda
- /dev/sdb
- /dev/sdc
If the myvg volume group already exists, the playbook adds the logical volume to the volume group.
If the myvg volume group does not exist, the playbook creates it.
The playbook creates an Ext4 file system on the mylv logical volume, and persistently mounts the file system at /mnt.

Additional resources

The /usr/share/ansible/roles/rhel-system-roles.storage/README.md file.

68.4.10.2. Additional resources

Managing local storage using RHEL System Roles

68.4.11. Removing LVM volume groups

This procedure describes how to remove an existing volume group.

Prerequisites

The volume group contains no logical volumes. To remove logical volumes from a volume group, see Removing LVM logical volumes.

Procedure

If the volume group exists in a clustered environment, stop the lockspace of the volume group on all other nodes. Use the following command on all nodes except the node where you are performing the removing:
```
# vgchange --lockstop vg-name
```
Wait for the lock to stop.

Remove the volume group:

# vgremove vg-name
  Volume group "vg-name" successfully removed

Additional resources

vgremove(8) man page

68.5. Modifying the size of a logical volume

After you have created a logical volume, you can modify the size of the volume.

68.5.1. Growing a logical volume and file system

This procedure describes how to extend the logical volume and grow a file system on the same logical volume.

To increase the size of a logical volume, use the lvextend command. When you extend the logical volume, you can indicate how much you want to extend the volume, or how large you want it to be after you extend it.

Prerequisites

You have an existing logical volume (LV) with a file system on it. Determine the file system type by using the df -Th command.
For more information on creating LV and a file system, see Creating LVM logical volume.
You have sufficient space in the volume group to grow your LV and file system. Use the vgs -o name,vgfree command to determine the available space.

Procedure

Optional: If the volume group has insufficient space to grow your LV, then add a new physical volume to the volume group by using the following command:
```
# vgextend myvg /dev/vdb3
Physical volume "/dev/vdb3" successfully created.
Volume group "myvg" successfully extended
```
For more information, see Creating LVM volume group.
Now that the volume group is large enough, execute any one of the following steps as per your requirement:
1. To extend the LV with the provided size, use the following command:
```
# lvextend -L 3G /dev/myvg/mylv
Size of logical volume myvg/mylv changed from 2.00 GiB (512 extents) to 3.00 GiB (768 extents).
Logical volume myvg/mylv successfully resized.
```
  Note
  You can use the -r option of the lvextend command to extend the logical volume and resize the underlying file system with a single command:
  # lvextend -r -L 3G /dev/myvg/mylv
  Warning
  You can also extend the logical volume using the lvresize command with the same arguments, but this command does not guarantee against accidental shrinkage.
2. To extend the mylv logical volume to fill all of the unallocated space in the myvg volume group, use the following command:
```
# lvextend -l +100%FREE /dev/myvg/mylv
 Size of logical volume myvg/mylv changed from 10.00 GiB (2560 extents) to 6.35 TiB (1665465 extents).
 Logical volume myvg/mylv successfully resized.
```
  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.

If you are not using the r option with the lvextend command to extend the LV and resize the file system with a single command, then resize the file system on the logical volume by using the following command:

xfs_growfs /mnt/mnt1/
meta-data=/dev/mapper/myvg-mylv  isize=512    agcount=4, agsize=65536 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1
data     =                       bsize=4096   blocks=262144, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 262144 to 524288

Note

Without the -D option, xfs_growfs grows the file system to the maximum size supported by the underlying device. For more information, see Increasing the size of an XFS file system.

For resizing an ext4 file system, see Resizing an ext4 file system.

Verification

Verify if the file system is growing by using the following command:

# df -Th
Filesystem            Type      Size  Used Avail Use% Mounted on
devtmpfs              devtmpfs  1.9G     0  1.9G   0% /dev
tmpfs                 tmpfs     1.9G     0  1.9G   0% /dev/shm
tmpfs                 tmpfs     1.9G  8.6M  1.9G   1% /run
tmpfs                 tmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup
/dev/mapper/rhel-root xfs        45G  3.7G   42G   9% /
/dev/vda1             xfs      1014M  369M  646M  37% /boot
tmpfs                 tmpfs     374M     0  374M   0% /run/user/0
/dev/mapper/myvg-mylv xfs       2.0G   47M  2.0G   3% /mnt/mnt1

Additional resources

vgextend(8), lvextend(8), and xfs_growfs(8) man pages

68.5.2. Shrinking logical volumes

You can reduce the size of a logical volume with the lvreduce command.

Note

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 system 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.

Warning

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.

Procedure

To shrink the mylv logical volume in myvg volume group to 64 megabytes, use the following command:

# lvreduce --resizefs -L 64M myvg/mylv
fsck from util-linux 2.37.2
/dev/mapper/myvg-mylv: clean, 11/25688 files, 4800/102400 blocks
resize2fs 1.46.2 (28-Feb-2021)
Resizing the filesystem on /dev/mapper/myvg-mylv to 65536 (1k) blocks.
The filesystem on /dev/mapper/myvg-mylv is now 65536 (1k) blocks long.

Size of logical volume myvg/mylv changed from 100.00 MiB (25 extents) to 64.00 MiB (16 extents).
 Logical volume myvg/mylv successfully resized.

In this example, mylv contains a file system, which this command resizes together with the logical volume.

Specifying the - sign before the resize value indicates that the value will be subtracted from the logical volume’s actual size. To shrink a logical volume to an absolute size of 64 megabytes, use the following command:
```
# lvreduce --resizefs -L -64M myvg/mylv
```

Additional resources

lvreduce(8) man page

68.5.3. Extending a striped logical volume

In order to increase the size of a striped logical volume, 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 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 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

You can create a stripe using the entire amount of space in the volume group.

# 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)

Note that the volume group now has no more free space.

# vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  vg     2   1   0 wz--n- 271.31G    0

The following command adds another physical volume to the volume group, which then has 135 gigabytes of additional space.

# 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

At this point you cannot extend the striped logical volume to the full size of the volume group, because two underlying devices are needed in order to stripe the data.

# 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

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

If you do not have enough underlying physical devices to extend the striped logical volume, it is possible to extend the volume anyway if it does not matter that the extension is not striped, which may result in uneven performance. When adding space to the logical volume, the default operation is to use the same striping parameters of the last segment of the existing logical volume, but you can override those parameters. The following example extends the existing striped logical volume to use the remaining free space after the initial lvextend command fails.

# 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

68.6. Customized reporting for LVM

LVM provides a wide range of configuration and command line options to produce customized reports and to filter the report’s output. For a full description of LVM reporting features and capabilities, see the lvmreport(7) man page.

You can produce concise and customizable reports of LVM objects with the pvs, lvs, and vgs commands. The reports that these commands generate include one line of output for each object. Each line contains an ordered list of fields of properties related to the object. There are five ways to select the objects to be reported: by physical volume, volume group, logical volume, physical volume segment, and logical volume segment.

You can report information about physical volumes, volume groups, logical volumes, physical volume segments, and logical volume segments all at once with the lvm fullreport command. For information on this command and its capabilities, see the lvm-fullreport(8) man page.

LVM supports log reports, which contain a log of operations, messages, and per-object status with complete object identification collected during LVM command execution. For further information about the LVM log report. see the lvmreport(7) man page.

68.6.1. Controlling the format of the LVM display

Whether you use the pvs, lvs, or vgs command determines the default set of fields displayed and the sort order. You can control the output of these commands with the following arguments:

You can change what fields are displayed to something other than the default by using the -o argument. For example, the following command displays only the physical volume name and size.
```
# pvs -o pv_name,pv_size
PV PSize
/dev/sdb1 17.14G
/dev/sdc1 17.14G
/dev/sdd1 17.14G
```

You can append a field to the output with the plus sign (+), which is used in combination with the -o argument.

The following example displays the UUID of the physical volume in addition to the default fields.

# 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

Adding the -v argument to a command includes some extra fields. For example, the pvs -v command will display the DevSize and PV UUID fields in addition to the default fields.

# 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

The --noheadings argument suppresses the headings line. This can be useful for writing scripts.
The following example uses the --noheadings argument in combination with the pv_name argument, which will generate a list of all physical volumes.
```
# pvs --noheadings -o pv_name
/dev/sdb1
/dev/sdc1
/dev/sdd1
```

The --separator separator argument uses separator to separate each field.

The following example separates the default output fields of the pvs command with an equals sign (=).

# 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

To keep the fields aligned when using the separator argument, use the separator argument in conjunction with the --aligned argument.

# 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

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 a full listing of display arguments, see the pvs(8), vgs(8) and lvs(8) man pages.

Volume group fields can be mixed with either physical volume (and physical volume segment) fields or with logical volume (and logical volume segment) fields, but physical volume and logical volume fields cannot be mixed. For example, the following command will display one line of output for each physical volume.

# 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

68.6.2. LVM object display fields

You can display additional information about the LVM objects with the pvs, vgs, and lvs commands.

A field name prefix can be dropped if it matches the default for the command. For example, with the pvs command, name means pv_name, but with the vgs command, name is interpreted as vg_name.

Executing the following command is the equivalent of executing pvs -o pv_free.

# pvs -o free
  PFree
  17.14G
  17.09G
  17.14G

Note

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$/".

Table 68.1, “The pvs Command Display Fields” 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.

Table 68.1. The pvs Command Display Fields
Argument	Header	Description
`dev_size`	DevSize	The size of the underlying device on which the physical volume was created
`pe_start`	1st PE	Offset to the start of the first physical extent in the underlying device
`pv_attr`	Attr	Status of the physical volume: (a)llocatable or e(x)ported.
`pv_fmt`	Fmt	The metadata format of the physical volume (`lvm2` or `lvm1`)
`pv_free`	PFree	The free space remaining on the physical volume
`pv_name`	PV	The physical volume name
`pv_pe_alloc_count`	Alloc	Number of used physical extents
`pv_pe_count`	PE	Number of physical extents
`pvseg_size`	SSize	The segment size of the physical volume
`pvseg_start`	Start	The starting physical extent of the physical volume segment
`pv_size`	PSize	The size of the physical volume
`pv_tags`	PV Tags	LVM tags attached to the physical volume
`pv_used`	Used	The amount of space currently used on the physical volume
`pv_uuid`	PV UUID	The UUID of the physical volume

By default, the pvs command displays the pv_name, vg_name, pv_fmt, pv_attr, pv_size and pv_free fields. The display is sorted by pv_name.

# 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

Using the -v argument with the pvs command adds the following fields to the default display: 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

You can use the --segments argument of the pvs command to display information about each physical volume segment. A segment is a group of extents. A segment view can be useful if you want to see whether your logical volume is fragmented.

The pvs --segments command displays the following fields by default: pv_name, vg_name, pv_fmt, pv_attr, pv_size, pv_free, pvseg_start, pvseg_size. The display is sorted by pv_name and pvseg_size within the physical volume.

# 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

You can use the pvs -a command to view devices detected by LVM that are not initialized as LVM physical volumes.

# 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

Table 68.2, “vgs Display Fields” 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.

Table 68.2. vgs Display Fields
Argument	Header	Description
`lv_count`	#LV	The number of logical volumes the volume group contains
`max_lv`	MaxLV	The maximum number of logical volumes allowed in the volume group (0 if unlimited)
`max_pv`	MaxPV	The maximum number of physical volumes allowed in the volume group (0 if unlimited)
`pv_count`	#PV	The number of physical volumes that define the volume group
`snap_count`	#SN	The number of snapshots the volume group contains
`vg_attr`	Attr	Status of the volume group: (w)riteable, (r)eadonly, resi(z)eable, e(x)ported, (p)artial and (c)lustered.
`vg_extent_count`	#Ext	The number of physical extents in the volume group
`vg_extent_size`	Ext	The size of the physical extents in the volume group
`vg_fmt`	Fmt	The metadata format of the volume group (`lvm2` or `lvm1`)
`vg_free`	VFree	Size of the free space remaining in the volume group
`vg_free_count`	Free	Number of free physical extents in the volume group
`vg_name`	VG	The volume group name
`vg_seqno`	Seq	Number representing the revision of the volume group
`vg_size`	VSize	The size of the volume group
`vg_sysid`	SYS ID	LVM1 System ID
`vg_tags`	VG Tags	LVM tags attached to the volume group
`vg_uuid`	VG UUID	The UUID of the volume group

The vgs command displays the following fields by default: vg_name, pv_count, lv_count, snap_count, vg_attr, vg_size, vg_free. The display is sorted by vg_name.

# vgs
  VG     #PV #LV #SN Attr   VSize  VFree
  new_vg   3   1   1 wz--n- 51.42G 51.36G

Using the -v argument with the vgs command adds the vg_extent_size and vg_uuid fields to te default display.

# 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

Table 68.3, “lvs Display Fields” 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.

Note

In later releases of Red Hat Enterprise Linux, the output of the lvs command may differ, with additional fields in the output. The order of the fields, however, will remain the same and any additional fields will appear at the end of the display.

Table 68.3. lvs Display Fields
Argument	Header	Description
* `chunksize` * `chunk_size`	Chunk	Unit size in a snapshot volume
`copy_percent`	Copy%	The synchronization percentage of a mirrored logical volume; also used when physical extents are being moved with the `pv_move` command
`devices`	Devices	The underlying devices that make up the logical volume: the physical volumes, logical volumes, and start physical extents and logical extents
`lv_ancestors`	Ancestors	For thin pool snapshots, the ancestors of the logical volume
`lv_descendants`	Descendants	For thin pool snapshots, the descendants of the logical volume
`lv_attr`	Attr	The status of the logical volume. The logical volume attribute bits are as follows: * Bit 1: Volume type: (m)irrored, (M)irrored without initial sync, (o)rigin, (O)rigin with merging snapshot, (r)aid, ®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, ®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. * Bit 4: fixed (m)inor * 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 * Bit 6: device (o)pen * 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_major`	KMaj	Actual major device number of the logical volume (-1 if inactive)
`lv_kernel_minor`	KMIN	Actual minor device number of the logical volume (-1 if inactive)
`lv_major`	Maj	The persistent major device number of the logical volume (-1 if not specified)
`lv_minor`	Min	The persistent minor device number of the logical volume (-1 if not specified)
`lv_name`	LV	The name of the logical volume
`lv_size`	LSize	The size of the logical volume
`lv_tags`	LV Tags	LVM tags attached to the logical volume
`lv_uuid`	LV UUID	The UUID of the logical volume.
`mirror_log`	Log	Device on which the mirror log resides
`modules`	Modules	Corresponding kernel device-mapper target necessary to use this logical volume
`move_pv`	Move	Source physical volume of a temporary logical volume created with the `pvmove` command
`origin`	Origin	The origin device of a snapshot volume
* `regionsize` * `region_size`	Region	The unit size of a mirrored logical volume
`seg_count`	#Seg	The number of segments in the logical volume
`seg_size`	SSize	The size of the segments in the logical volume
`seg_start`	Start	Offset of the segment in the logical volume
`seg_tags`	Seg Tags	LVM tags attached to the segments of the logical volume
`segtype`	Type	The segment type of a logical volume (for example: mirror, striped, linear)
`snap_percent`	Snap%	Current percentage of a snapshot volume that is in use
`stripes`	#Str	Number of stripes or mirrors in a logical volume
* `stripesize` * `stripe_size`	Stripe	Unit size of the stripe in a striped logical volume

The lvs command provides the following display by default. The default display is sorted by vg_name and lv_name within the volume group.

# lvs
  LV     VG              Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  origin VG              owi-a-s---    1.00g
  snap   VG              swi-a-s---  100.00m      origin 0.00

A common use of the lvs command is to append devices to the command to display the underlying devices that make up the logical volume. This example also specifies the -a option to display the internal volumes that are components of the logical volumes, such as RAID mirrors, enclosed in brackets. This example includes a RAID volume, a striped volume, and a thinly-pooled volume.

# lvs -a -o +devices
  LV               VG            Attr       LSize   Pool   Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices
  raid1            VG            rwi-a-r---   1.00g                                      100.00           raid1_rimage_0(0),raid1_rimage_1(0)
  [raid1_rimage_0] VG            iwi-aor---   1.00g                                                       /dev/sde1(7041)
  [raid1_rimage_1] VG            iwi-aor---   1.00g                                                       /dev/sdf1(7041)
  [raid1_rmeta_0]  VG            ewi-aor---   4.00m