TrilioVault uses Cinder snapshots for calculating full and incremental backups.
For full backups, TrilioVault creates Cinder snapshots for all the volumes in the backup job. It then leaves these Cinder snapshots behind for calculating the incremental backup image during next backup.
During an incremental backup operation it creates new Cinder snapshots, calculates the changed blocks between the new snapshots and the old snapshots that were left behind during full/previous backups. It then deletes the old snapshots but leaves the newly created snapshots behind.
So, it is important that each tenant who is availing TrilioVault backup functionality has sufficient Cinder snapshot quotas to accommodate these additional snapshots. The guideline is to add 2 snapshots for every volume that is added to backups to volume snapshot quotas for that tenant.
You may also increase the volume quotas for the tenant by the same amount because TrilioVault briefly creates a volume from snapshot to read data from the snapshot for backup purposes.
During a restore process, TrilioVault creates additional instances and Cinder volumes. To accommodate restore operations, a tenant should have sufficient quota for Nova instances and Cinder volumes. Otherwise restore operations will result in failures.