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1.7. Issues with Live Migration of VMs in a RHEL cluster
Information on support policies for RHEL high availability clusters with virtualized cluster members can be found in Support Policies for RHEL High Availability Clusters - General Conditions with Virtualized Cluster Members. As noted, Red Hat does not support live migration of active cluster nodes across hypervisors or hosts. If you need to perform a live migration, you will first need to stop the cluster services on the VM to remove the node from the cluster, and then start the cluster back up after performing the migration.
The following steps outline the procedure for removing a VM from a cluster, migrating the VM, and restoring the VM to the cluster.
Note
Before performing this procedure, consider the effect on cluster quorum of removing a cluster node. For example, if you have a three node cluster and you remove one node, your cluster can withstand only one more node failure. If one node of a three node cluster is already down, removing a second node will lose quorum.
- If any preparations need to be made before stopping or moving the resources or software running on the VM to migrate, perform those steps.
- Move any managed resources off the VM. If there are specific requirements or preferences for where resources should be relocated, then consider creating new location constraints to place the resources on the correct node.
- Place the VM in standby mode to ensure it is not considered in service, and to cause any remaining resources to be relocated elsewhere or stopped.
pcs cluster standby VM
# pcs cluster standby VMCopy to Clipboard Copied! Toggle word wrap Toggle overflow - Run the following command on the VM to stop the cluster software on the VM.
pcs cluster stop
# pcs cluster stopCopy to Clipboard Copied! Toggle word wrap Toggle overflow - Perform the live migration of the VM.
- Start cluster services on the VM.
pcs cluster start
# pcs cluster startCopy to Clipboard Copied! Toggle word wrap Toggle overflow - Take the VM out of standby mode.
pcs cluster unstandby VM
# pcs cluster unstandby VMCopy to Clipboard Copied! Toggle word wrap Toggle overflow - If you created any temporary location constraints before putting the VM in standby mode, adjust or remove those constraints to allow resources to go back to their normally preferred locations.
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