1.4. LVM Logical Volumes in a Red Hat High Availability Cluster
- High availability LVM volumes (HA-LVM) in an active/passive failover configurations in which only a single node of the cluster accesses the storage at any one time.
- LVM volumes that use the Clustered Logical Volume (CLVM) extensions in an active/active configurations in which more than one node of the cluster requires access to the storage at the same time. CLVM is part of the Resilient Storage Add-On.
1.4.1. Choosing CLVM or HA-LVM
- If multiple nodes of the cluster require simultaneous read/write access to LVM volumes in an active/active system, then you must use CLVMD. CLVMD provides a system for coordinating activation of and changes to LVM volumes across nodes of a cluster concurrently. CLVMD's clustered-locking service provides protection to LVM metadata as various nodes of the cluster interact with volumes and make changes to their layout. This protection is contingent upon appropriately configuring the volume groups in question, including setting
locking_typeto 3 in the
lvm.conffile and setting the clustered flag on any volume group that will be managed by CLVMD and activated simultaneously across multiple cluster nodes.
- If the high availability cluster is configured to manage shared resources in an active/passive manner with only one single member needing access to a given LVM volume at a time, then you can use HA-LVM without the CLVMD clustered-locking service
1.4.2. Configuring LVM volumes in a cluster
- For a procedure for configuring an HA-LVM volume as part of a Pacemaker cluster, see An active/passive Apache HTTP Server in a Red Hat High Availability Cluster in High Availability Add-On Administration. Note that this procedure includes the following steps:
- Configuring an LVM logical volume
- Ensuring that only the cluster is capable of activating the volume group
- Configuring the LVM volume as a cluster resource