Microsoft Hyper-V VSS Writer problem
Configuration
Host: Windows Server 2008 R2 SP1 (x64)
Guests: Windows Server 2008 R2 SP1 (x64)
Problem/Symptoms
Windows Server Backup fails when guests are active:
Log Name: Microsoft-Windows-Backup
Source: Microsoft-Windows-Backup
Date: 5/20/2012 12:40:59
Event ID: 9
Task Category: None
Level: Error
Keywords:
User: SYSTEM
Computer: host.local-domain.com
Description:
The backup operation that started at ‘2012-05-20T16:38:15.428000000Z’ 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.
When guest machines are not active, the backup finishes OK.
On host machine, in an elevated command prompt I executed:
C:\Windows\system32>vssadmin list writers
vssadmin 1.1 – Volume Shadow Copy Service administrative command-line tool
(C) Copyright 2001-2005 Microsoft Corp.
[…]
Writer name: ‘Microsoft Hyper-V VSS Writer‘
Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
Writer Instance Id: {0447e7f8-be3c-4f11-a5b6-0aa3155c06fb}
State: [5] Waiting for completion
Last error: Unexpected error
[…]
It shows that there is a problem with Hyper-V VSS Writer.
Related articles:
- General troubleshooting: http://blogs.technet.com/b/filecab/archive/2009/09/16/diagnosing-failures-in-windows-server-backup-part-1-vss-spp-errors.aspx
- Issue identification: http://support.microsoft.com/kb/2004712
Solution (1)
- Based on link 2 above:
During an online backup Volume Shadow Copy Service (VSS) requires mounting the snapshotted VHDs in order to revert them back to their proper state. If automount is disabled, VSS cannot mount the snapshotted VHDs as required.
To determine if automount is enabled run DISKPART.EXE from a command prompt, and then run the following command at the DISKPART prompt:
automount
which shows that disks are not automounted
2. In elevated command prompt type:
MountVol /E
This may fix the issue so that Windows Server Backup works fine on the host machine.
Solution (2)
Solution (2) is for the same symptoms as Solution (1), but (probably) for different cause.
Try to determine which virtual machine causes the problem: save or shut down one VM at a time and see if you are able to successfully perform manual backup.
I had a case when one of the VMs had full disk, with almost no free space.
Once I cleaned up disk and released some space, the VM stopped making backup problems.
