KB975354: W2008 R2 Hyper-V Rollup for CSV and VSS

Cluster Shared Volume (CSV) is the shared storage system that can be used by multiple cluster members at once for storing and running virtual machines in a Hyper-V cluster.  CSV is specifically customised for Hyper-V and should not be used for anything else – you even have to agree to than to enable it.  That customisation means that things would change a bit.

VSS is the Volume Shadow Copy Service.  Using Hyper-V certified backup solutions like DPM you can backup the state of a virtual machine running in Hyper-V in a supported manner.  This is done at the host level.  That’s different to a file level backup that you would do with an agent installed in the VM.  That would be able to recover individual files.  The host level backup would be able to recover the entire VM back to the point of time that you did the backup.

There have been reports of issues.  For example, DPM 2007 R2 is not live migration aware.  You’ll have to wait until around April for DPM 2010 for a solution to that.  That only affects the snapshot backups.

A rollup package has been released by Microsoft for Windows Server 2008 R2 Hyper-V to resolve some issues with CSV and VSS.  Thanks to Hans Vredevoort (clustering MVP) for making me aware of this.  Article KB975354 fixes the following situations.

“This update rollup package resolves some issues that occur when you backup or restore Hyper-V virtual machines

Issue 1

Consider the following scenario:

  • Some Internet SCSI (iSCSI) connections are created in a virtual machine that is running Windows Server 2003.
  • You back up this virtual machine on the virtual machine host server.

In this scenario, the error code 0x800423f4 occurs when you back up the virtual machine. Additionally, the following event is logged into the Hyper-V Virtual Machine Management Service event log:

The number of reverted volumes does not match the number of volumes in the snapshot set for virtual machine "’virtual machine name’ (Virtual machine ID <GUID>)".

Issue 2

Consider the following scenario:

  • Cluster shared volumes are enabled on a failover cluster for Hyper-V.
  • Some virtual machines are saved on the same volume. But they are running on different nodes.
  • These virtual machines are backed up in parallel.

In this scenario, the virtual machine backup operation fails.

Issue 3

Consider the following scenario:

  • A virtual machine is being backed up on a server that is running Hyper-V.
  • At the same time, an application backup operation is being performed in the same virtual machine.

In this scenario, some data is truncated from the application backup in the virtual machine. Therefore, this behaviour causes data loss.

Issue 4

Consider the following scenario:

  • A virtual machine that has some snapshots is backed up on a server that is running Hyper-V.
  • Then, this virtual machine is restored to another location.

In this scenario, the restore operation fails and the virtual machine may be corrupted”.

If you’re running a Windows Server 2008 R2 Hyper-V cluster and are still getting used to it then there’s some good news.  Here’s how I’ll approach this:

  • Put the OpsMgr 2007 agent for host 1 into maintenance mode.
  • Put the host 1 in maintenance mode in VMM 2008 R2.  That kicks off live migration and moves VM’s from that host to another host.  You can do this manually in the failover cluster management console if you don’t have VMM 2008 R2.
  • Apply the update to host 1 and reboot.
  • Test host 1 with a test VM.
  • Repeat with all other hosts in the cluster.

That should work.  And it’ll probably be your first opportunity to use Live Migration and VMM 2008 R2 Maintenance Mode in anger.  Think about it, when do you normally get to do server patching during the work day?  Now you can!

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