View source for Migrate-volume-block-migration


== Add Support for Volume migration during Live (block) migration ==

'''External Specification:'''

Add --block-device-mapping parameter to "nova live-migration --block_migrate" command. 

The entire format of the command will be like this

`nova live-migration --block-migrate --block-device-mapping vda=1:::0, --block-device-mapping vdb=...(all attached EBS volumes) <instance_name> <name_of_destination_compute_node>`

Administrator has to specify --block-device-mapping parameters for all volumes attached to the instance.

Follow the existing format to specify block device mapping

`--block-device-mapping <device_name>=<a>:<b>:<c>:<d>`

    <device_name>: device name referred from the instance

    <a>: destination volume uuid (Note: MUST specify an '''existing volume''', must be same size to the source volume)

    <b>: N/A

    <c>: N/A or size of the volume

    <d>: 0:Do not delete the source volume, 1:delete the source volume

'''Note:''' Volumes on the destination volume node need to be created before the migration takes place.
The migration could ensure copying the data onto the destination volumes.

'''Example:'''
* Instance1 has two cinder volumes (created on cinder-node1) attached at vol-a on vdc (1gb) ,vol-b on vdb (3gb) (compute-node1).
* Instance1 is to be migrated to compute-node2.
* Create two (1gb vol-c, 3gb vol-d) volumes on cinder-node2.
* run : "nova live-migration --block-migrate --block-device-mapping vda=<vol-c uuid>::1:0 vdb=<vol-d uuid>::3:0 <Instance1 uuid> compute-node2.
* All data in vol-a is copied to vol-c by nova/libvirt's migrateToURI.
* All data in vol-b is copied to vol-d by nova/libvirt's migrateToURI.