Nova Migration Type

The migration types are:

Non-live migration (sometimes referred to simply as ‘migration’)
The instance is shut down for a period of time to be moved to another hypervisor. In this case, the instance recognizes that it was rebooted.

Live migration (or ‘true live migration’)
Almost no instance downtime. Useful when the instances must be kept running during the migration.
The different types of live migration are:

2-1. Shared storage-based live migration.

Both hypervisors have access to shared storage.

2-2. Block live migration

No shared storage is required. Incompatible with read-only devices such as CD-ROMs and Configuration Drive (config_drive).

2-3. Volume-backed live migration

Instances are backed by volumes rather than ephemeral disk, no shared storage is required, and migration is supported (currently only available for libvirt-based hypervisors).

What's this?

2-3. Volume-backed live migration の Nova instance のAZ間の Migration

Nova instance (running 状態) を別の AZの Hypervisor (Compute node) へ移動
Nova instance の Boot Volume は Cinder に格納
Cinder は Shared Storage

[Case]

Cinder volume を接続していない場合
Cinder volume を接続している場合

[Case1] Migrate Nova instance (w/o Cinder volume)

Initial state

Hypervisor (Compute node)

# nova hypervisor-list
+----+-----------------------+
| ID | Hypervisor hostname   |
+----+-----------------------+
| 6  | node-27 |
| 9  | node-28 |
| 15 | node-31 |
+----+-----------------------+

AZ

# nova availability-zone-list | egrep -A 10 "^\| nova"
| nova                     | available                              |
| |- node-27               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:40:02.000000 |
| |- node-28               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:39:55.000000 |
| nova2                    | available                              |
| |- node-31               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:40:02.000000 |
+--------------------------+----------------------------------------+

Nova instance is on node-28

# nova list --field name,status,,OS-EXT-STS:vm_state,OS-EXT-AZ:availability_zone,OS-EXT-SRV-ATTR:hypervisor_hostname
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| ID                                   | Name       | Status |  | OS-EXT-STS: Vm State | OS-EXT-AZ: Availability Zone | OS-EXT-SRV-ATTR: Hypervisor Hostname |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| ed831ace-39ef-4960-8bae-a035d292c305 | admin_vm01 | ACTIVE |  | active               | nova                         | node-28                              |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

Boot volume of Nova instance is in Cinder

# nova show admin_vm01 | egrep "Property|image|os-extended-volumes:volumes_attached"
| Property                             | Value                                                    |
| image                                | Attempt to boot from volume - no image supplied          |
| os-extended-volumes:volumes_attached | [{"id": "5a272756-ab0c-4311-a1ce-3f1736d167df"}]         |

Cinder list

# cinder list
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+
|                  ID                  |   Status  | Display Name | Size | Volume Type | Bootable |             Attached to              |
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+
| 5a272756-ab0c-4311-a1ce-3f1736d167df |   in-use  | admin_vol01  |  1   |     None    |   true   | ed831ace-39ef-4960-8bae-a035d292c305 |
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+

Migrate Nova instance

Migration from node-28 of AZ:nova to node-31 of AZ:nova2

# nova live-migration admin_vm01 node-31

Check the migration result

Nova instance is moved from node-28 of AZ:nova to node-31 of AZ:nova2

# nova list --field name,status,,OS-EXT-STS:vm_state,OS-EXT-AZ:availability_zone,OS-EXT-SRV-ATTR:hypervisor_hostname
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| ID                                   | Name       | Status |  | OS-EXT-STS: Vm State | OS-EXT-AZ: Availability Zone | OS-EXT-SRV-ATTR: Hypervisor Hostname |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| ed831ace-39ef-4960-8bae-a035d292c305 | admin_vm01 | ACTIVE |  | active               | nova2                        | node-31                              |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

Cinder status

# nova show admin_vm01 | egrep "Property|image|os-extended-volumes:volumes_attached"
| Property                             | Value                                                    |
| image                                | Attempt to boot from volume - no image supplied          |
| os-extended-volumes:volumes_attached | [{"id": "5a272756-ab0c-4311-a1ce-3f1736d167df"}]         |

# cinder list
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+
|                  ID                  |   Status  | Display Name | Size | Volume Type | Bootable |             Attached to              |
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+
| 5a272756-ab0c-4311-a1ce-3f1736d167df |   in-use  | admin_vol01  |  1   |     None    |   true   | ed831ace-39ef-4960-8bae-a035d292c305 |
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+

[Case2] Migrate Nova instance (w/ Cinder volume)

Initial State

Hypervisor (Compute node)

# nova hypervisor-list
+----+-----------------------+
| ID | Hypervisor hostname   |
+----+-----------------------+
| 6  | node-27               |
| 9  | node-28               |
| 15 | node-31               |
+----+-----------------------+

AZ

# nova availability-zone-list | egrep -A 10 "^\| nova"
| nova                     | available                              |
| |- node-27               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:40:02.000000 |
| |- node-28               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:39:55.000000 |
| nova2                    | available                              |
| |- node-31               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:40:02.000000 |
+--------------------------+----------------------------------------+

Nova instance is on node-28

# nova list --field name,status,,OS-EXT-STS:vm_state,OS-EXT-AZ:availability_zone,OS-EXT-SRV-ATTR:hypervisor_hostname
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| ID                                   | Name       | Status |  | OS-EXT-STS: Vm State | OS-EXT-AZ: Availability Zone | OS-EXT-SRV-ATTR: Hypervisor Hostname |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| 8e6a33c1-1564-4d63-8964-f10a6d66e2c2 | admin_vm01 | ACTIVE |  | active               | nova                         | node-28                              |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

Boot volume of Nova instance is in Cinder
Nova instance has one additional Cinder volume

# nova show admin_vm01 | egrep "Property|image|os-extended-volumes:volumes_attached"
| Property                             | Value                                                                                            |
| image                                | Attempt to boot from volume - no image supplied                                                  |
| os-extended-volumes:volumes_attached | [{"id": "5a272756-ab0c-4311-a1ce-3f1736d167df"}, {"id": "7bf75168-8370-45f8-b1c5-e65926605960"}] |