The November 2012 cumulative rollup for Windows 8 and Windows Server 2012 contains a fix for a when you get the following error when backing up Windows Server 2012 Hyper-V VMs that are stored on NetApp storage:
The number of volumes reverted does not match the number of volumes in the snapshot set for virtual machine.
This cumulative update provided a new version of the Integration Components on the host to fix the issue. You have (or had if you have already done it) to deploy this new version of the ICs to your guest OSs. Didier Van Hoye previously (and correctly) blogged that this was only necessary for guest OSs that are Windows Server 2008 & Windows Vista or later.
To get the fix: patch your host (Windows Update – KB2770917) and update the ICs in the guest OSs.
Note: I record this as KB2770917. That’s the number of the cumulative update that was delivered via Windows Update. That update includes a number of articles that are not publicly documented. We just got briefed on this issue so that’s why I’m posting this article 5 months after the update release.