Restrictions on the temporary storage location for the Windows System State and System backup image file

Article ID
5017
Last Reviewed Date
Product Version
AhsayOBM: 7.3 or above
Operating System
Windows
Description

This Know-How article explains the restrictions imposed by Microsoft's Windows Server Backup Feature (WSB) on the storage location for the MS Windows System and System State Backup module.

Solution

For System State backup (MS Windows System State Backup module), the target volume CANNOT be a:

  • Critical Volume (by default)

    Critical volumes refers to the volumes present on the system which house the operating system and other files which are essential for the OS to function properly. In the event of a disaster these volumes are required to bring your server back up and running.

  • Source Volume (by default)

    Source volume is any volume that contain a file that is included in the backup (e.g. component selected to be included in the system state data by the WSB during the backup, you do not have the option to exclude any file).

  • Network Share (limitation for Windows Server 2008 only)

    Network share refers to a Universal Naming Convention (UNC) path to a remote shared folder.

This restriction only implies to Windows Server 2008. For Windows Server 2008 R2 or above, the target volume can be a network share.

To change the default behavior to allow the target to be a critical or source volume, add the 'AllowSSBToAnyVolume' registry entry to the target server. Refer to the technote for details:

https://support.microsoft.com/kb/944530

There are known issues with storing a system state backup on a source volume:

  • Backup can fail, the backup may be modified during the backup process, which might cause the backup to fail.
  • It causes an inefficient use of target space.
    Twice the amount of space is necessary for a backup than for the original data. The volume must allocate twice the amount of space for the shadow copy process.

For System backup (MS Windows System Backup module), the target volume CANNOT be a:

  • Critical Volume

    Critical volume refers to the volumes present on the system which house the operating system and other files which are essential for the OS to function properly. In the event of a disaster these volumes are required to bring your server back up and running.

  • Source Volume

    Source volume is any volume that is selected for backup (e.g. volume selected in the backup source setting).

Unlike System State backup, no registry change can workaround these restrictions.

For both System and System state backup, the target volume CANNOT be a subdirectory on a local volume.

Windows Server Backup will enforce system and system state data to a 'WindowsImageBackup' folder on the root of the local volume:

{backuptarget}:\WindowsImageBackup

Summary table of all restrictions:

  System System State
Critical Volume No Yes
Non-Critical Volume Yes Yes
USB Volume Yes Yes
Network Share Yes Yes
Sub-Directory No No
Source Volume No Yes
For optimal backup performance, it is strongly recommended to use a dedicated local volume for temporary storage of the Windows System Backup and Windows System State image file.