Add two optional parameters to specify availability_zone and volume_type for cinder backup restore API to better support backup and restore across availability zones.
Backup across availability_zones is a typical scenario for disaster recovery: say, backup driver located in AZ-1 is configured to backup data to backup backend located in AZ-2. When AZ-1 crashes, user tries to restore volume from the backup data located in AZ-2. It would be useful to provide parameters for user to specify the availability_zone and the volume_type of the restore volume.
The availability_zone parameter will enable user to create a restore volume to a specified availability_zone where the backup data is actually located. The geographical locality will enhance the performance for restore copy.
While with the volume_type parameter, the backup restore API can provide more options for user to create a restore volume, say, with rbd backup backend, compared with LVM, user could choose to restore to a rbd volume, where restore will do diff copy instead of full copy and thus enhance restore efficiency.
Currently, when user makes a request to restore a backup without volume_id, the backup-restore API will create a restore volume with default volume_type and default availability_zone.
As the availability_zone is none, cinder scheduler will randomly pick up one availability_zone to create this restore volume. In one typical disaster recovery scenario described above, restore volume with randomly selected availability_zone may locate in an availability_zone geographically far away from backup data. In this way, restore might fail if the restore side backup driver could not access backup data across availability_zones. Even if backup driver could access backup data remotely, cross-wan IO will cause a performance penalty. No matter for the sake of correctness or efficiency, user would like to have control of specifying the availability_zone of restore volume.
Without volume type option, the restore volume will be created with default volume type and thus default volume backend. Since the default volume backend may not understand the backup data format, the backup driver may not be able to take the most efficient way to restore from the backup data but will do a full copy. It is better to give user more options to enhance restore performance.
There are customers who want to restore a backup in a certain backend and availability_zone without any restore volume. The customers can specify the volume_type and availability_zone to restore this backup.
In order to solve this problem, we add two optional parameters to specify volume_type and availability_zone for the backup-restore API. The volume_type parameter is to specify the volume backend of the restore volume. The availability_zone parameter is to specify the availability_zone where the restore volume would locate in. Thus, user could choose restore volume type according to backup backend and choose restore volume location geographically close to the backup data location. This change will give user more options to ensure restore correctness and enhance restore performance.
Ensure type and AZ are included in the restore.start notification.
End user will be able to restore a backup with specified volume_type and availability_zone.
This might allow cross-az restore scenarios that weren’t possible before, which might cause network performance degradation.
The deployer will be able to restore a backup with specified volume_type and availability_zone.
Unit tests and tempest tests will be provided.