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?

2 Answers 2


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

  • Hi, I don't get that error message you stated. I will backup the registry before editing it. I will also try a registry cleaner.
    – GurdeepS
    May 2, 2010 at 16:42
  • 2
    Do NOT try a "registry cleaner". These are scams. You should know better as a developer.
    – rmalayter
    Jun 16, 2011 at 13:13

Is there anything in the Windows application event log, with a source value of VSS? That might have a more specific error message than what backupassist is giving you.

Otherwise, I'd give what Holocryptic said a shot. Just some helpful pointers -

To get vshadow.exe -

  • for Windows Server 2003 (or Windows XP) - download VSS SDK 7.2.
  • for Windows Server 2008 (or Windows Vista) - download Windows SDK v6.1.
    On that page you may see it telling you to download the Windows 7/.NET Fx 3.5 SP1 SDK instead - do not do this. The vshadow.exe version in that SDK is incompatible with Windows Server 2008.

If you see the error message,

The procedure entry point ClusterGetVolumeNameForVolumeMountPoint 
could not be located in the dynamic link library RESUTILS.dll

you have downloaded the wrong version.

for Windows Server 2008 R2 (or Windows 7), you need to download Windows SDK v7.0.

When installing the Windows SDK, you can untick all the documentation and compiler options to save space and time. You just need the Win32 Samples I think.

Once the Windows SDK is installed, vshadow.exe will be located in,

  • x86 - C:\Program Files\Microsoft SDKs\Windows\vx.x\bin\vsstools\vshadow.exe
  • x64 - C:\Program Files\Microsoft SDKs\Windows\vx.x\bin\x64\vsstools\vshadow.exe

where vx.x is either v6.1 or v7.0.

You can just copy vshadow.exe; it doesn't depend on anything else in the Windows SDK.

All this said, the new way of managing shadow copies is via diskshadow.exe, which is in-built into Windows Server 2008 and 2008 R2. Its interface is similar to diskpart, in that it has its own little shell, as opposed to vshadow.exe which acts as a simple command line app.

  • I don't know how this applies to the question, but the details in this post were exactly what I was looking for! (Which components to install and what path there would at to get vshadow.exe) Thanks!
    – Orangutech
    Jul 29, 2011 at 23:25

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