BackupAssist and Hyper-V – where’s that error coming from?

We’ve seen a noticeable increase over the past few months in the number of customers performing Hyper-V backups using BackupAssist, so I’m hoping some of you will find it useful to hear about an issue we helped resolve recently.

The customer was running BackupAssist on their Hyper-V host system and had initially been performing a backup of the system state and some data which was working fine, when they added the Hyper-V guest machines though, it produced this error each time:

ERROR – A Volume Shadow Copy Service operation error has occurred

A quick check of the VSS writers showed the following:

Writer name: ‘Microsoft Hyper-V VSS Writer’

   Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}

   Writer Instance Id: {59e80baa-4691-4036-868a-6af912180e19}

   State: [5] Waiting for completion

   Last error: Unexpected error

Initially restarting the VSS writer service didn’t help and only a reboot of the server would restore the writer to a “No error” state, however as soon as the backup was run, the error would reappear.

To resolve the issue, we needed to look at the virtual guest machines individually and in listing the VSS writers we finally came across one which was showing an error in the “SPSearch4” writer.  This is actually a well known issue for which we have a Knowledge Base article, and once we resolve this issue the backup completed successfully.

So, the next time you have an issue with Hyper-V backups, remember that it could well be the guest machines that are the root of the problem even though the error is showing on the host.

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