Hyper-V VSS Writer Fails

[guest]

Anyone have an issue where you cannot backup the windows 2008 host with Hyper-V?

When the backup starts my VMs go to saved/running/saved/running and get stuck in that loop until the Windows backup fails after 30 minutes

All errors in event logs point to VSS and when I run the "vssadmin List writers" command I get this:

Writer name: 'Microsoft Hyper-V VSS Writer'
Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
Writer Instance Id: {849ac9f6-2996-440b-b26d-1c3c9ab49876}
State: [8] Failed
Last error: Retryable error

I have tried rebooting and that has not solved the issue.

I need to install the RTM Hyper-V update- but I would like to get a successful host server backup before I do that.

I was thinking of aside from performing flat file copies of the Guests while they are shutdown- that I maybe able to get a good backup if all the machines are shutdown- but I am not sure if the Hyper-V VSS writer is updated with the RTM version of Hyper-V or if there are some other things I could do to solve this.

I have 2 other machines configured just like this one without issue.

Thanks,

[guest]

I am afraid this error message cannot help. Please take a look at the Event Viewer, at Windows Logs\Application, see if any errors or warnings exist relating to VSS or Backup.



If possible, please also try shutting down these VMs and then try the backing up so that we can narrow down the root cause. In addition, shutting down these VMs, then rebooting the host machine may resolve this issue.



A very possible cause is that the virtual hard disk of the VM is being written when you performed the backup, and by some unknown reasons, it cannot reach the "consistent" state. The normal procedure of backing up a running VM is saving/restoring the VM, by using the Windows Server Backup feature, even when you have IS installed. This is to ensure the disk is in a "consistent" state and, this procedure should work well in common scenarios.



If possible, would you please try the following steps to see if it can help? This is one method to ensure running VMs can be backed up via Windows Server Backup. However, we do not recommend this method at this time. If you want to back up the running VM, use the System Center Data Protection Manager (DPM, fow now it doesn't support Hyper-V, but will come with SP1) or some other third-party backup applications that can work with Hyper-V VSS writer.



Note that you should always back up the Registry before changing it so that once you encounter any problems, you can restore it.



1. Open the Registry Editor (regedit.exe).

2. Navigate to the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion

3. Create a new registry key, under the CurrentVersion key, and name the new key WindowsServerBackup .

4. Create a new registry key, under the WindowsServerBackup key created above, and name the new key Application Support .

5. Create a new registry key, under the Under the Application Support created above, and name the new key {66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE} .



6. Click to highlight the new {66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE} key. This GUID stands for the relevant Hyper-V VSS writer.

7. Click the Edit menu option in Registry Editor, select New > String Value, and create the following value:

Value name: Application Identifier
Value type: REG_SZ
Value data: Hyper-V



8. Exit Registry Editor.



I hope this can help.



Best regards,
Chang Yin

[guest]

Yes, the backup should be successful. However, if you have a VM with more than two snapshots, you may encounter an error that you cannot restore the whole server. The workaround is:



1. Delete the VM.

2. Use “Files and Folder” restore option to restore the “Snapshots” folder.

3. Initiate “Application” restore.



The Hyper-V VSS writer should has already been registered on the operating system. The cause that you didn't see it after running "vssadmin list writers" command might be that, you didn't start the Virtual Machine Management Service. However, Hyper-V VSS writer doesn't register with Windows Server Backup feature. If you want to back up your whole server by Windows Server Backup (though we don't recommend it for now), you need to manually register it by adding the registry keys.



Best regards,

Chang Yin