I recently came across an issue in an environment where we used DPM 2012 SP1 to backup Windows Server 2012 Virtual Machines running on Server 2008R2 Hyper-V cluster. The only option available in DPM for the VM’s was “Backup Using Saved State”.
Of course this is not the preferred method for backing up a VM because it will be put in a saved state during backup causing the VM to be offline for that period of time. I’d like to use the online backup option: “Backup Using Child Partition Snapshot”.
After some digging I found a forum post which had a reply from a Microsoft employee that suggested to create the following registry key:
REG_DWORD ScopeSnapshots 0x0
After implementing the registry key on all of the Windows Server 2012 VM’s I could backup using a child partition snapshot without any problems.
It seems that the Hyper-V integration components need a new feature in Windows Server 2012 (and Windows 8) called scoped VSS snapshots to be turned off in order to support online backups. This feature is enabled by default.
I also found some reports about Windows Server 2012 guests transferring the whole VM during backups instead on block level changes. Implement the registry key on every VM that is Windows 8 or Windows Server 2012 to resolve both of these issue.