Add incremental backup/restore support for Cinder VMware VMDK volume driver

Cinder VMware VMDK volume driver does not have support for incremental backup. As the size of the VMDK volume grows and the changes to volume between backups tend to be low, performing full backups on the volume may become resource intensive. This proposal suggests following flags to existing VMware VMDK volume drive to support incremental backup functionality.

1. Perform incremental backup

cinder backup-create <volumeid> —snapshot —incr <full/incr backup container>

This CLI takes a snapshot of the volume and uploads only the changes in vmdk since last full/incr backup to swift. Again at the end of the backup, the snapshot will be deleted.

Incremental backup can record changed block since last full/incr backup and all incremental backup must originate from the base full backup. In order to keep the deltas manageable size, user can periodically take full backups and then do incremental.

2. Perform incremental restore

cinder restore-create <volumeid> —snapshot —incr <full/incr backup container>

The CLI takes a snapshot of the volume and restore full/incr to target vmdk. Again at the end of the restore, the snapshot will be deleted.

Perform an incremental restore must start with a base full backup data and then sequentially restore the incremental backup data.