Openstack VM live migration can occur through block live migration without shared storage, shared storage based live migration using technologies like GlusterFS, or volume backed VM live migration where VMs are booted from volumes on shared storage. Block live migration copies VM disks over the network during migration, taking longer than methods using shared storage which allow faster migration by leaving disks on storage accessible from both source and destination hosts.

1. Openstack VM live migration

2. • Openstack VM live migration can have 3
categories:
• Block live migration without shared storage
• Shared storage based live migration
• Volume backed VM live migration

3. Block live migration
• Block live migration does not require shared
storage among nova-compute nodes
• it uses network(TCP) to copy VM disk from
source host to destination host,
• it takes longer time to complete than shared
storage based live migration.
• it takes longer time to complete than shared
storage based live migration.

4. Shared storage based live migration
• GlusterFS as shared storage for nova-compute
nodes
• Since VM disk is stored on shared storage,
hence live migration much much more faster
than block live migration.

5. Volume backed VM live migration
• VMs booted from volume can be also easily
and quickly migrated just like shared storage
based live migration since both cases VM disks
are on top of shared storages.