I came across an issue today where I wanted to use DPM 2010 to backup a number of virtual machines that were running on a non-clustered Hyper-V host but which had the HP P4000 Left Hand Hardware VSS Writer installed on it.
When I added the Virtual Machines to my protection group and ran a Hyper-V backup of those VM's, this is the error that came back to me after a few minutes
Affected area: \Backup Using Child Partition Snapshot\ -VMM2012
Occurred since: 08/09/2011 11:33:07
Description: The replica of Microsoft Hyper-V \Backup Using Child Partition Snapshot\-VMM2012 on VMHOST1-SRV. is inconsistent with the protected data source. All protection activities for data source will fail until the replica is synchronized with consistency check. You can recover data from existing recovery points, but new recovery points cannot be created until the replica is consistent.
For SharePoint farm, recovery points will continue getting created with the databases that are consistent. To backup inconsistent databases, run a consistency check on the farm. (ID 3106)
Failure occurred while adding one or more of the volumes involved in backup operation to snapshot set. Please check the event log on VMHOST1-SRV. to troubleshoot the issue. (ID 30290 Details: Internal error code: 0x80990A00)
Check recent records from the VolSnap source in the Application Event Log to find out why the problem occurred.
Synchronize with consistency check.
Resolution: To dismiss the alert, click below
Now at this point, I remember reading back when DPM 2010 was released that it would always default to try and use a hardware VSS writer if it was present on the Hyper-V host first instead of using the built in System VSS writer.
This is by design and a pretty good design too in fairness as it is the best way to backup the VM's your CSV's in your Hyper-V cluster.
I didn't want to have to go through the hassle of troubleshooting why the HP P4000 Left Hand hardware VSS writer wasn't working and I didn't want to uninstall it as we were using other volumes on that server that would need it.
All I wanted was a quick way to backup the VM's using the built in System VSS writer in Windows Server and I decided to write up a quick blog post on it - as much for my own reference as anyone elses!
Logon to the Hyper-V host (or hosts) that you are trying to backup using the System VSS Writer with an administrative account.
Open up the server registry using 'Regedit'
Browse to the following location in the registry:
HKLM\Software\Microsoft\Microsoft Data Protection Manager\Agent
Now when you get to this point, right mouse click on the 'Agent' key folder and then select 'New' and then highlight 'Key' and click 'Enter' (see the screenshot below)
This will now create a new subkey underneath the 'Agent' key
Rename this subkey to:
You should now have a registry key structure like the screen below on your Hyper-V host
Once you have completed these simple steps, re-run or synchronize the DPM protection group that contains the virtual machines on the Hyper-V host you have just modified and it will complete successfully this time!!
Make sure that if you want to use the System VSS writer on all of your Hyper-V hosts that you add the above registry key to each one. It is also worth noting that if you are not using a Hardware VSS Writer, then you will need to configure serialization of your Hyper-V backups, otherwise the virtual machine backups within each protection group will fail randomly due to lack of access to the Cluster Shared Volume.
Here's a great link on how to configure CSV serialization:
One final point to note is that this process is irrelevant if the Hyper-V host has no Hardware VSS writers installed in the first place as DPM 2010 will then just try to use the System VSS writer instead.