Can I Live Migrate an Instance Across Availability Zones?

Problem

• Live migration of instance across availability zone is failing
• Below messages are reported in logs

/var/log/nova/nova-conductor.log

WARNING nova.scheduler.utils [...] Failed to compute_task_migrate_server: No valid host was found

/var/log/nova/nova-scheduler.log

INFO nova.scheduler.host_manager [...] Host filter only checking host [...] and node [hostname]INFO nova.filters [...] Filter AvailabilityZoneFilter returned 0 hosts

Environment

• Platform9 Managed OpenStack - All versions
• Nova

Cause

Live migration of instance is possible across the availability zone but only using CLI. As we can see both the source and destination host are part of different availability zones.

• • Source Host

$ openstack compute service list | grep [UUID]| 50 | nova-compute    | [UUID] | Test-AZ | enabled  | up    | 2020-XX-XXTYY:YY:YY.000000 |

- Destination Host

$ openstack compute service list | grep [UUID]| 69 | nova-compute    | [UUID] | nova       | enabled  | up    | 2020-XX-XXTYY:YY:YY.000000 |

Resolution

• Live migration between different availability zones works with the --force parameter to live-migration. Migrating instances using --force option, can forcefully bypass the nova-scheduler and move an instance to a specified host.

$ nova live-migration [--block-migrate] [--force] [server] [[host]]

Additional Information

Refer the OpenStack documentation for more details on the Availability Zones.