VSS error 521 when attempting backup

vsswindows-server-2008windows-server-2008-r2

I have backupassist and I attempt to run a backup, with VSS service running. However, I get this error in Windows Event Log:

The backup operation that started at
'‎2010‎-‎04‎-‎30T01:51:15.601000000Z' has failed because the Volume
Shadow Copy Service operation to create a shadow copy of the volumes
being backed up failed with following error code '2155348129'. Please
review the event details for a solution, and then rerun the backup
operation once the issue is resolved.

Code: 521.

The error in backupassist is:

The backup operation stopped before completing. Detailed error: ERROR
– A Volume Shadow Copy Service operation error has occurred: (0x80042336) The writer experienced a partial failure. Check the
component level error state for more information.

Log of files successfully backed up:
C:\Windows\Logs\WindowsServerBackup\Backup-29-04-2010_18-51-15.log
Log of files for which backup failed:
C:\Windows\Logs\WindowsServerBackup\Backup_Error-29-04-2010_18-51-15.log

A Volume Shadow Copy Service operation failed. Please check "VSS" and
"SPP" application event logs for more information. ERROR – A Volume
Shadow Copy Service operation error has occurred: (0x80042336) The
writer experienced a partial failure. Check the component level error
state for more information.

Any idea how to fix this? I work in a company with server engineers, they all state of having no problems with 2008 and VSS (though in the company we use predominantly 2003). Without VSS working, I assume no backup application will work?

Best Answer

Try running the DOS command "vssadmin list writers" and "vss admin list providers". Capture the output of these command, as they will help in debugging the issue. If a particular writer reports any unexpected state, search the web for conditions that may be causing this issue.

A quick way to reset the writers is to reboot the server.

If VSS errors continue to persist, try re-registering VSS. Follow the steps outlined in MS KB article 940184. Doublecheck for other VSS providers, i.e. any backup software that installs any sort of Open File agent (examples would be St Bernard, older versions of Backup Exec Open File Option, etc). These can be shown by typing "vssadmin list providers" at a command prompt. Providers from uninstalled software can be deleted by removing the offending CLSID of the VSS provider and rebooting the machine.

Is the machine a 64-bit machine? Are you getting "A function call was invalid because of the state of either the backup extensions or the coordinator. For example calling AddToSnapshot set prior to calling StartSnapshotSet." ? If so, try deleting the Subscription key per MS KB 940184 

  1.    Click Start, click Run, type Regedit, and then click OK.
  2.    Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\EventSystem\{26c409cc-ae86-11d1-b616-00805fc79216\Subscriptions
  3.    On the Edit menu, click Delete, and then click Yes to confirm that you want to delete the subkey.
  4.    Exit Registry Editor.
  5.    Reboot the machine

Next you can try running a utility called vshadow. It's part of the windows SDK.

To do a single manual snapshot, run 

vshadow [drive letter]

which would take and immediately destroy a VSS snapshot of C: and D:. If that works, VSS is probably OK; if not it's a VSS problem.

All of this is where I would start to troubleshoot VSS problems.

As with anything, be extremely careful when modifying the registry

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