Can I used thin-provisioned LUNs as backing storage for my High Availability cluster?
Environment
- Red Hat Enterprise Linux 7, 8, 9, 10 (with the High Availability or Resilient Storage Add on)
pacemaker
Issue
- Is it possible to utilize thin-provisioned LUNs as a backing storage for a RHEL cluster?
Resolution
A pacemaker cluster supports thin-provisioned logical volumes when the resource-agents LVM or LVM-activate are configured in active/passive configuration. This means that the volume group that contains the thin-provisioned logical volumes is only activated on one node at a time.
Limitations
[Thin-provisioned logical volumes](https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Logical_Volume_Manager_Administration/LV.html#thinly_provisioned_volume_creation) is **not supported** when one or more of the following is true:
- When the volume group that contains the thin-provisioned logical volumes have the
c(clustered) ors(shared) bit enabled - When the volume group that contains the thin-provisioned logical volumes are configured in active/active configuration.
Root Cause
When utilizing thinly provisioned logical volumes, this allows you to create logical volumes that are larger than the currently available extents. A thin pool can be utilized for storage management, and the storage can be allocated to an arbitrary number of devices when needed. Devices can then be created that are bound to the thin pool for other allocations when programs and applications actually write to the thinly provisioned logical volume.
LVM thin-provisioning is only supported on a pacemaker cluster when the volume group (and logical volume) are configured in a active/passive configuration.
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