So I will start by a step by step guide on how I recently set this up and what worked for me.
Install the HP Application aware snapshot manager version 126.96.36.1994 and then enter the credentials for the saniq management group. In the image below there are 2 sans a p4300 and p4500
Then test the credentials
Then Delete the %Programfiles%\Microsoft DPM\DPM\Config\DataSourceGroups.xml file from the DPM server.
Add this dword value to the dpm server with a value of 2
HKLM\Software\Microsoft\Microsoft Data Protection Manager\2.0\Configuration\MaxAllowedParallelBackups
I then create a protection group for hyper-v virtual machines and create a protection group per clustered shared volumes.Another thing which i have found to work quite well is to have all virtual machines on 1 clustered shared volume to be managed by one node and then the other clustered shared volume will be managed by another node.So when the scheduled DPM protection group runs it speaks to the hardware vss writer which then speaks to the lefthand san which takes a snapshot.You can use System Center Virtual Machine Manager to migrate storage if required.
If you take a look at the management group within San IQ , You will see the snapshot being created and deleted when the protection group completes it's backup.Also during a scheduled protection group's backup if you look in the monitoring tab and jobs in progress you will notice excellent throughput on the running backup job.
Always make sure you have enough space on your Lefthand sans for snapshots.
And the end result is healthy protection groups.