How to Migrate an Instance with Zero Downtime: OpenStack Live Migration with KVM Hypervisor and NFS Shared Storage
http://www.mirantis.com/blog/tutorial-openstack-live-migration-with-kvm-hypervisor-and-nfs-shared-storage/
http://www.mirantis.com/blog/tutorial-openstack-live-migration-with-kvm-hypervisor-and-nfs-shared-storage/