Backup Version and Space Management in Windows Server Backup

Read this link for more details
http://blogs.technet.com/filecab/archive/2009/06/22/backup-version-and-space-management-in-windows-server-backup.aspx

How to get backup versions
Wbadmin get versions -backupTarget:

How to delete non-system state backups
Windows Server Backup deletes a backup by just deleting the corresponding shadow copy and updating the backup catalog. You can perform the same steps manually to delete backups on demand. However, the backup catalog update cannot be done manually and it will happen instead during the next backup. In short, to delete a backup version manually, you need to delete the corresponding shadow copy from the backup storage location.

To delete a shadow copy, follow these general steps:

- Identify the backup version you want to delete by querying the backup versions on your backup storage location.
- Determine the shadow copy ID of the version you want to delete.
- Delete the shadow copy.

The following command line lists all shadow copies on a specified backup storage location:

Vssadmin list shadows /for=

For example, to list the shadow copies on the location Y, type:

Vssadmin list shadows /for=Y:

On Windows Server 2008 R2, the shadow copy ID is same as Snapshot ID given in the output of querying backups. On Windows Server 2008, you can find your backup’s shadow copy ID by looking at output of Vssadmin list shadows /for=. Match the shadow copy creation time with your backup’s Backup time value.

Delete the Shadow Copy for the specific Shadow Copy ID:

1. To open a command prompt with elevated privileges, click Start, right-click Command Prompt, and then click Run as administrator. Then type:

DiskShadow.exe

2. Type:

Delete shadows ID

3. To exit DiskShadow type:

Exit

To delete the oldest shadow copy on backup storage location, type the following command in step 2 above:

Delete shadows OLDEST

For example, if your storage location is volume G:, type:

Delete shadows OLDEST G:

If you have scheduled backups to dedicated disks, Windows Server Backup doesn’t assign a drive letter to the backup storage location to avoid any accidental data write or loss of backups. In that case, you can use the GUID of the backup storage volume to delete the oldest shadow copy. You can get volume GUIDs for all volumes on your system by using the Mountvol command. If your scheduled backup storage location is a dedicated disk, it will be reported with No Mount Points in the output of Mountvol. The volume GUID is in {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} format.

Then, to delete the oldest shadow copy on that volume, type:

Delete shadows OLDEST \\?\Volume{GUID}

For example, for a volume GUID of 7fc1871b-2e1f-11dd-a339-001e4fb7af35, type:

Delete shadows OLDEST \\?\Volume{7fc1871b-2e1f-11dd-a339-001e4fb7af35}