Criteria for deleting backups

To avoid reaching the limit of 255 Snapshot copies per volume, you should delete the backups that you no longer need. You can delete backups by using either the age-based criteria or the quantity-based criteria.

Age-based Snapshot copy deletion: You can delete backups that are assigned to a particular backup management group and that are older than a specified number of days. You can specify the deletion criteria by selecting the “Delete backups older than” option. Enter the number of days for which you want to keep the most recent backups for the backup management group.

Quantity-based Snapshot copy deletion: You can delete backups that are assigned to a particular backup management group so that only a specified number of backups remain for that backup management group. Specify the deletion criteria by selecting the “Delete (oldest) backups in excess of” option. Enter the number of the most recent backups that you want to keep for the backup management group.

Note: Automatic deletion of older backups in a management group is the recommended method for managing the number of Snapshot copies stored on your system.

When SnapManager counts the number of stored backups, it also counts the backups that are shared by multiple Storage Groups. Therefore, more backups than you specify in the “Delete backups older than” or “Delete backups in excess of” box are retained.

For example, assume that you back up Storage Groups A and B. Both reside on the same volume and contain the following backup sets.

Backup set	Description
Storage Group A
exchsnap__orbit3_01-23-2006_16.21.07	Old backup—good
exchsnap__orbit3__recent	Recent backup—good
Storage Group B
exchsnap__orbit3_01-23-2006_16.21.07	Old backup—good
exchsnap__orbit3__recent	Recent backup—inconsistent

You set the “Delete backups in excess of” box to 2 to preserve the most recent two backup sets.

To preserve two good backups for Storage Group B, SnapManager does not delete the Snapshot copy exchsnap__orbit3_01-23-2006_16.21.07, which is old and good. Therefore, because both Storage Groups reside on the same volume, three backups for Storage Group A remain instead of two.