Snapshots of Hyper-V VM with DPM fails on new cluster node

Scenario
After adding a new node (4^th) to an existing Hyper-V Cluster, DPM backup jobs failed on VM’s that where hosted on the new node.
For this cluster I use hardware snaphots on a Dell Equallogic SAN. So the “HIT Kit” from Dell was installed on the server and all the other required components to get this running. But unfortunately as soon as I placed a VM on the new node, the DPM snapshots failed. The message on the DPM server was:
Failed to prepare a Cluster Shared Volume (CSV) for backup as another backup using the same CSV is in progress. (ID 32612 Details: Back up is in progress. Please wait for backup completion before trying this operation again (0x8007173D))

Solution
This error is confusing because it normally means that you haven’t serialized the backup of the VM’s on the cluster and/or the MaxAllowedParallelBackups key was not set. This was all done. So that couldn’t be the case.
What I noticed was that when we initiated a backup, there was no snapshot created on the Equallogic. I checked that the Equalogic VSS writer was available on the server (with the “VSSADMIN LIST PROVIDERS” command). No problem there.
Next step was to run a Cluster Validation Report with the Failover Cluster Manager.

In this report there was a warning for the new node and the CSV volumes: “This node is not a possible owner for this resource”. You cannot add a cluster node as a possible owner for CSV volumes via the Failover Cluster Manager so I had to go with the command prompt:

• First check the list of possible owners:
  cluster res ‘name of resource’ /listowners
  I checked in my case the 2 CSV volumes.
• Add the new node to the list:
  cluster res ‘name of resource’ /addowner:’missing node’
  Also did this for both of the CSV volumes.

I ran the Cluster Vaildation Report again and the warning was gone. So I tried a backup with DPM and as a miracle this worked as well J.

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