Installation guide

Chapter 1. Red Hat Cluster Suite Overview 19

Figure 1-14. GFS and GNBD with Directly Connected Storage

1.6. Cluster Logical Volume Manager

The Cluster Logical Volume Manager (CLVM) provides a cluster-wide version of LVM2.

CLVM provides the same capabilities as LVM2 on a single node, but makes the volumes

available to all nodes in a Red Hat cluster. The logical volumes created with CLVM make

logical volumes available to all nodes in a cluster.

The key component in CLVM is clvmd. clvmd is a daemon that provides clustering ex-

tensions to the standard LVM2 tool set and allows LVM2 commands to manage shared

storage. clvmd runs in each cluster node and distributes LVM metadata updates in a clus-

ter, thereby presenting each cluster node with the same view of the logical volumes (refer

to Figure 1-15). Logical volumes created with CLVM on shared storage are visible to all

nodes that have access to the shared storage. CLVM allows a user to conﬁgure logical vol-

umes on shared storage by locking access to physical storage while a logical volume is

being conﬁgured. CLVM uses the lock-management service provided by the cluster infras-

tructure (refer to Section 1.3 Cluster Infrastructure).