DPM 2012 SP1 RU2 - Huge System Volume Information folder

If you face the following behavior in DPM 2012 SP1 RU2: "Huge System Volume Information folder while backing up high available Hyper-V VMs", you need to delete the dpmfilter files and update the servers with the below hotfixes.

To get to a clean state, please delete the DpmFilter* files from “System Volume Information” using the following steps:

1. On an elevated command prompt:
2. fltmc unload DpmFilter (on all cluster nodes)
From one of the Cluster nodes
3. psexec -s cmd          
( psexec is sysinternal tool, used to run cmd under system account)
4. In this command prompt (running as system):
5. cd C:\ClusterStorage
6 . for /d %i in (volume*) do del /s
"%i\System Volume Information\DpmFilter*"
(* includes DPMFilterBitmap{Guid}, DPMFilterStatus, DPMFilterLog, DPMFilterTrace*)
7. verify files are deleted by “dir /s /b DpmFilter*”
8. exit
Then load the filter again on all nodes
9. fltmc load DpmFilter (on all cluster nodes)
Run DPM Consistency check to re-start normal protection.

You will also need to make sure, that you have the latest updates for Windows Server 2012 Hyper-V cluster. Please see:

2878635 - Update is available that improves the resiliency of the cloud service provider in Windows Server 2012: December 2013
https://support.microsoft.com/kb/2878635