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. 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