Why Does the Used Capacity of a Vault Change Only Slightly After I Deleted Unwanted Backups?

Symptoms

After unwanted backups are deleted from the vault, the used capacity of the vault decreases by only 1 GB to 2 GB.

Possible Causes

The backup mechanism of CBR:

• By default, CBR performs a full backup for a resource for the first time and backs up all used data blocks. All subsequent backups are incremental. An incremental backup backs up only the data blocks changed since the last backup.
• Each incremental backup is a virtual full backup. Correlated data blocks are indexed by using pointers.
• When you delete a backup, no matter manually or automatically, only data blocks that are not referenced by other backups will be deleted.

Figure 1 Backup mechanism