Backup completes successfully with VSS errors

Backup jobs complete successfully with Volume Shadow Copy Service (VSS) errors in the Windows application log on the Hyper-V host.

Symptoms

When performing backups using the Virtual Server Agent (VSA) for Hyper-V, backup jobs complete successfully but Volume Shadow Copy Service (VSS) errors appear in the Windows application log on the Hyper-V host. For example:

Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface... Access is denied.

Volume Shadow Copy Service error: Failed resolving account Administrator with status 1376. Check connection to domain controller and VssAccessControl registry key.

Causes

This issue can occur in Windows Server 2008 R2 when the backup operation does not provide access to the VSS writer from the network service account. These errors do not prevent the backup from completing successfully, and can be ignored.

Resolution

To prevent these errors from being written to the Windows application log on the Hyper-V host:

1. Log on to the Hyper-V server on which the VSS errors appear
2. Add NETWORK SERVICE into the Backup Operators group (in Windows 2008 R2: Computer Management | System Tools | Local Users and Groups | Groups | Backup Operators | Properties | Add). This step is not necessarily required; but it eliminates the possibility that network service access issues would produce the VSS errors.
3. Open a command line using Run as Administrator, and run the following commands: **net stop cryptsvc

sc config cryptsvc type= own

net start cryptsvc** 4. Test the backup operation again.