DPM 2012 R2 U3 and Windows Server 2012 R2 U1.

It's possible that I installed U3 after it was working. I'll check that.

Yes, DPM does not mount the snaps. The snaps are mounted on the hyper-v hosts.

As I understand, you will still gain some performance, because the virtual machine snaps could be merged after the volume snap is created. After the backup the volume snap would be deleted.

Without the hardware snap the virtual machine snaps have to be merged after the backup finishes, which could take some time and would make the merge slower.

The info I got:

DPM Backups today need Volume snapshot to get the stable copy of Application

•            DPM now with Windows Server 2012 R2 can use VM snapshot to Backup instead of volume snapshot

•             Volume Snapshot is avoided using Dummy VSS provider (DPM Null Provider)

•             HyperV has made changes to give DPM and App consistent VM snapshot.

•             Backups are done from Live Volume

•             Hardware or software provider are not necessary anymore as DPM does not need volume snapshot.

Only Applicable to HyperV over Windows Server 2012 R2

•             Prereq - support.microsoft.com/.../2919355

•             Used only  for CSV volume and Remote SMB. Not used for NTFS, REFS etc.

•             Installed along with agent as separate service (VssNullProvider)

•             Production Server Needs Reboot after patch installation before Null provider can work.

•             “Vssadmin list providers” can be used to confirm the installation

VSS Provider priority in DPM

•             Null Provider (default, can be disabled using Regkey)

•             Software provider (if forced using Regkey)

•             Default Provider (can be software or hardware)

To disable Null provider (on production server)

reg add "HKLM\Software\Microsoft\Microsoft Data Protection Manager\Agent" /v UseNullProvider /t REG_DWORD /d 0 /f