System State backup failing, backup has warnings about Space or Veto


System State backup failing, backup has warnings



System State backup failing; Windows 7 backup has warnings about skipped files and System State backup failed and/or VSS_E_INSUFFICIENT_STORAGE or VSS_E_PROVIDER_VETO.



Solution 1 - command line: Ensuring the Shadow Storage has been set up correctly

To see the amount of storage space allocated and used for Volume Shadow Copies run the following command from a command prompt with elevated privileges:

vssadmin list shadowstorage

 If you do not see the the storage listed, you need to add it (change the C: to the drive letter):

vssadmin add ShadowStorage /For=C: /on=C: /MaxSize=20%

If it already exists, but it says UNBOUNDED (means all of remainder), change it to 20%

vssadmin Resize ShadowStorage /For=C: /On=C: /MaxSize=20%

Unmounted/System volumes

For system unmounted partitions that are read only, i.e. system restore or boot volumes, assign to C: or disk with available space for 600mb allotment. This has been shown to assist with clearing VSS_E_PROVIDER_VETO unable to flush I/O write errors. Due to complexity of unmounted volume's naming convention GUI interface for setup is more efficient. 

Solution 1 - gui: Ensuring the Shadow Storage has been set up correctly

Increase limit to 20% of disk space. In above example the default is 10% so double listed entry for each data volume. 

Solution 2: Clearing the Shadow Storage

During normal Windows operation, restore points will be created during software installation and other day to day operational tasks.  These restore points create snapshots that reside in an area of the disk and consume disk space. Sometimes Windows has an internal error and cannot delete the storage. This disk space can be reclaimed by using the vssadmin command in an elevated (Administrator) MS-DOS Command Prompt.  Once the command prompt is loaded, enter the following commands.

To verify that multiple snapshots exists that exceed the range of your Backup Chain Set, execute this command: vssadmin list shadows

 WARNING: Do not run the delete or resize command if the computer is pending a reboot due to Windows Updates!

Once you have rebooted the server and you confirm that the snapshot issue exists, execute this command to delete snapshots:

To delete the oldest only: 

vssadmin delete shadows /For=C: /oldest

To delete all shadows:

vssadmin delete shadows /all

This will remove all VSS snapshots on the system, prompting you first for confirmation. Running the command 'vssadmin list shadows' will display a list of snapshots on your system along with associated ID.  Deletion by ID must specify a valid snapshot ID, deletion by volume must specify a valid Windows volume (e.g.: C:) and deletion of oldest snapshot simply removes the single, oldest snapshot on the system.  An example of deleting by ID follows:

vssadmin delete shadows /shadow={42bb9090-723c-4107-8954-92006026defd}

To not be prompted by any of the commands use the /quiet flag.

On some systems, the command vssadmin delete shadows isn't available.

  • In Windows XP VSS snapshots can't be persistent on XP (a reboot will get rid off them)
  • Vista/2008 you can delete shadows by reducing the size of the ShadowStorage: resize shadowstorage /On=C:/3GB

To resize the space reserved for ShadowStorage (NOTE: change the C: to the drive letter):

vssadmin Resize ShadowStorage /For=C: /On=C: /MaxSize= 20%
   ...OR if the computer doesn't accept percentages
vssadmin Resize ShadowStorage /For=C: /On=C: /MaxSize=350MB

Once you complete your changes, we recommend you run a new 1-Time Full/Master to synchronize the new baseline data, and after the backup completes, you can run the new child backup that your schedule is based on.


ShadowStorage size not large enough


For more detailed information on backup failures and performance issues see Unitrends KB 5062 - Backup Failures and Performance Issues

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