Virtual machine live migration

About live migration

Live migration is the process of moving a running virtual machine instance (VMI) to another node in the cluster without interrupting the virtual workload or access. If a VMI uses the LiveMigrate eviction strategy, it automatically migrates when the node that the VMI runs on is placed into maintenance mode. You can also manually start live migration by selecting a VMI to migrate.

You can use live migration if the following conditions are met:

  • Virtual machines must have a persistent volume claim (PVC) with a shared ReadWriteMany (RWX) access mode to be live migrated.

  • The pod network binding must not be of the bridge interface type ().

  • Live migration is supported for virtual machines that are attached to an SR-IOV network interface.

  • If the virtual machine uses a host model CPU, live migration is supported only between nodes that support the virtual machine’s host model CPU.

Updating access mode for live migration

For live migration to function properly, you must use the ReadWriteMany (RWX) access mode. Use this procedure to update the access mode, if needed.

Procedure

  • To set the RWX access mode, run the following oc patch command:

    1. $ oc patch -n openshift-cnv \
    2.     cm kubevirt-storage-class-defaults \
    3.     -p '{"data":{"'$<STORAGE_CLASS>'.accessMode":"ReadWriteMany"}}'

Additional resources: