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?

2-1. Shared storage-based live migration の AZ 間

Nova instance (running 状態) を別の AZ の Hypervisor (Compute node) へ移動

[Case]

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

[条件]

Shared Storage あり
移動する際に Target Hypervisor (Compute node) を指定

[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 :-) 2015-02-24T08:01:42.000000 |
| |- node-28               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:01:45.000000 |
| nova2                    | available                              |
| |- node-31               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:01:42.000000 |
+--------------------------+----------------------------------------+

Nova instance is on node-27 of AZ:nova

# 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 |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| 25fc9e72-1236-4580-b103-0edc5520ee8e | admin_vm01 | ACTIVE |  | active               | nova                         | node-27                              |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

Migrate Nova instance

Migration from node-27 to node-31

# nova live-migration admin_vm01 node-31

Check the migration result

Nova instance is moved from node-27 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 |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| 25fc9e72-1236-4580-b103-0edc5520ee8e | admin_vm01 | ACTIVE |  | active               | nova2                        | node-31                              |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

[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 :-) 2015-02-24T08:01:42.000000 |
| |- node-28               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:01:45.000000 |
| nova2                    | available                              |
| |- node-31               |                                        |
| | |- nova-compute        | enabled :-) 2015-02-24T08:01:42.000000 |
+--------------------------+----------------------------------------+

Nova instance is on node-28 of AZ:nova

# 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 |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
| e08aa732-5af9-417e-a577-95495da77da1 | admin_vm01 | ACTIVE |  | active               | nova                         | node-28                              |
+--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

With Cinder volume

# cinder list
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+
|                  ID                  |   Status  | Display Name | Size | Volume Type | Bootable |             Attached to              |
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+
| 41dc0b12-b7fd-4ae7-b77e-478c97ee308c |   in-use  | admin_vol01  |  1   |     None    |  false   | e08aa732-5af9-417e-a577-95495da77da1 |
+--------------------------------------+-----------+--------------+------+-------------+----------+--------------------------------------+

# cinder show admin_vol01 | egrep "Property|availability_zone"
|            Property            | Value                   |
|       availability_zone        | nova                    |

# nova show admin_vm01 | egrep "Property|volumes_attached"
| Property                             | Value                                                    |
| os-extended-volumes:volumes_attached | [{"id": "41dc0b12-b7fd-4ae7-b77e-478c97ee308c"}]         |

Instance

$ ssh cirros@{INSTANCE} lsblk
NAME   MAJ:MIN RM    SIZE RO TYPE MOUNTPOINT
vda    253:0    0      1G  0 disk
`-vda1 253:1    0 1011.9M  0 part /
vdb    253:16   0      1G  0 disk
`-vdb1 253:17   0   1023M  0 part /mnt/vol01

$ ssh cirros@{INSTANCE} df -h /mnt/vol01/
Filesystem                Size      Used Available Use% Mounted on
/dev/vdb1              1006.9M     17.3M    938.5M   2% /mnt/vol01

Migrate Nova instance

Migration from node-28 to node-31

# 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 |
    +--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+
    | e08aa732-5af9-417e-a577-95495da77da1 | admin_vm01 | ACTIVE |  | active               | nova2                        | node-31                              |
    +--------------------------------------+------------+--------+--+----------------------+------------------------------+--------------------------------------+

Cinder status

    $ ssh cirros@{INSTANCE} lsblk
    NAME   MAJ:MIN RM    SIZE RO TYPE MOUNTPOINT
    vda    253:0    0      1G  0 disk
    `-vda1 253:1    0 1011.9M  0 part /
    vdb    253:16   0      1G  0 disk
    `-vdb1 253:17   0   1023M  0 part /mnt/vol01

Instance

    $ ssh cirros@{INSTANCE} df -h /mnt/vol01/
    Filesystem                Size      Used Available Use% Mounted on
    /dev/vdb1              1006.9M     17.3M    938.5M   2% /mnt/vol01

Environment

Openstack : Juno
Ceph : Firefly

Reference

Nova Migration (non live migration) to Different Hypervisor
Nova Migration (non live migration) to Different Hypervisor between AZ
Nova Migration (true live migration) to Different Hypervisor
Nova Migration (true live migration) to Different Hypervisor between AZ
Nova Migration (Manually) between AZ
Nova Migration (Manually) between Region
Nova Migration (true live migration) to Different Hypervisor - Volume-backend live migration (instance)
Nova Migration (true live migration) to Different Hypervisor - Volume-backend live migration (instance) between AZ