SnapVault for NetBackup uniquely identifies each backup based on the policy, client, and the time at which the backup was taken. Each backup for a specific client-policy pair is uniquely stored in a Snapshot copy referred to as an archival Snapshot copy.
The following information applies only to FSE backups. Each Snapshot copy can store backups of many different client-policy pairs.
Data ONTAP software keeps the minimum number of Snapshot copies required to capture every backup uniquely in a Snapshot copy.
In the following example, multi-streaming is not used.
Example: You have a policy that backs up two clients, client_1 and client_2, in the same secondary volume. After a backup to client_1, Data ONTAP creates a Snapshot copy (for example, Snap_1) to preserve it. A backup to client_2 follows. After the backup to client_2, Data ONTAP creates another Snapshot copy (for example, Snap_2) to store it. The backup to client_2 occurred after the backup to client_1, therefore Snap_2 contains both backups. Data ONTAP can delete Snap_1 because the backup to client_1 is also preserved in Snap_2.
A subsequent backup to client_1 results in the creation of another Snapshot copy (for example, Snap_3). However, Snap_3 and Snap_2 both need to be preserved because they contain two different backups to the same client (client_1).