VM snapshots and Pure
In order to perform backups, Archiware Pure needs to both create and remove VMware created VM snapshots.
In order to guarantee a clean VM state, before a backup starts Archiware Pure will first delete old backup snapshots. In versions prior to 2.0.3, this includes deleting all VM snapshots. This assures that virtual disks can be consolidated if necessary and that Changed Block Tracking can be enabled or reset if needed.
Since version 2.0.3, snapshot management in Pure has been improved so that all snapshots are no longer deleted every time. Before each backup, Pure will search the VM for any leftover backup snapshots and will delete those snapshots only. Other snapshots won't be affected.
Another reason for deleting all snapshots is if the Changed Block Tracking is not enabled before backup. In order to enable incremental backups, the CBT feature needs to be activated and this requires that all snapshots be removed from a VM. Because Pure no longer deletes all snapshots automatically, if the CBT is supported but not enabled, you will have to manually remove all VM snapshots. Until all snapshots are removed, Pure will not be able to perform incremental backups for this VM so all backups will be full.
Having achieved the valid VM state, Pure will proceed with backup process. During backup, Pure will create a new VM snapshot named BackupSnapshot. This snapshot will be removed when the backup finishes. In case the backup process was interrupted (e.g. by a power outage), this snapshot will be removed before next backup as described above.