update June 2013:
at June 19 I blogged about another update released by Microsoft which solved several storage related issues. Read more here.
Microsoft customers using Windows Server 2012 Hyper-V had serious issues when back-ups were made of virtual machines running on CSV volumes of Windows Server 2012 Hyper-V hosts.
Virtual machine enters a paused state or a CSV volume goes offline when you try to create a backup of the virtual machine on a Windows Server 2012-based failover cluster. This issue also occurs when you try to create a snapshot of the virtual machine by using a backup software that uses the Microsoft Software Shadow Copy Provider
This happens with any backup tool including Microsoft Data Protection Manager 2012 SP1 and Veeam Backup & Recovery v6.5
Initially Microsoft released a hotfix which was supposed to solve this issue. However applying the hotfix resulted in a serious memory leak which could lead to no available memory for virtual machines.
Background information on this can be read at Hyper-v.nu , Technet forum and SCDPM blog of Matthijs Vreeken.
At Saturday February 16 the Windows team has released a V2 of the fix to address CSV backup issues and is available for download. This will address the known memory leak issue along with some other issues that were discover during testing.
This fix supersedes the original fix and includes all fixes contained in the original.
Virtual machine enters a paused state or a CSV volume goes offline when you try to create a backup of the virtual machine on a Windows Server 2012-based failover cluster.
Download the hotfix at http://support.microsoft.com/kb/2813630
The Windows team is investigating other issues found during testing and not included in this release. However they wanted to get this fix published since the memory leak issue is fixed and provide immediate relief.