If you are running a Hyper-v Role on Server 2008 R2 (not tested on Hyper-v 2012) and you have a Windows 8 or Server 2012 running as guest OS (virtual machine) you may have a problem when trying to execute a VSS backup snapshot of the whole server (including its VMs). For example using Windows Server Backup or Acronis or Storage Craft Shadow Protect etc.
It will do the backup, but while doing it, it will put above mentioned virtual machines into “Saved” state, making them unusable during the backup process.
The Windows 8 or Windows server 2012 guest needs to have scoped VSS snapshots turned off in order to support online backups. This is a new feature apparently in Win8/2012 and the default is enabled.
Implement this registry key on EACH Windows 8 or Windows 2012 guest to resolve the issue. You must add a key called SystemRestore, then add a value called ScopeSnapshots as follows.
Run>regedit>HKLM\Software\Microsoft\Windows NT\CurrentVersion\ > create key SystemRestore > Create DWORD ScopeSnapshots > value 0