Live migration

One of the key tenets of cloud is being abstracted away from hardware. However, hardware does require maintenance from time to time, or a host will need a software upgrade. Whatever the reason, a host may need to be taken offline for maintenance, ideally with little to no downtime for the instances running on the host. To accommodate this, Nova provides two methods for live migrating instances: block migration, when shared storage is not available in the environment, and the live migration flag, when instances are booted from the shared storage (where every compute host can see the same storage used by each instance for its boot volume).

Getting ready

To live migrate an instance, you will need the following information:

• The openstack command-line client

• The openrc file containing appropriate administrator credentials

• The name of the instance

• The name of the destination hypervisor

Note

If your environment is configured so that instances boot from the shared storage, such as RBD provided...