2.4. 群集逻辑卷管理器（CLVM）

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：

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

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

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”.

图 2.2 “CLVM 总览” shows a CLVM overview in a cluster.