Hyper-V 2012 Failover Cluster: Live Migration Fails

I love hyper-v. I especially love hyper-v running on windows server 2012 in a failover cluster configuration. It truly is a wonderful environment to administer windows servers. With this said, the error logging leaves a lot to be desired.

I've just spent the better part of two days trying to work out why live migration of servers between cluster nodes wasn't working. The error message which Microsoft helpfully give you when this happens is simply:

Event ID: 21502
Source: Hyper-V High Availability
’Virtual Machine <VM NAME>’ Live Migration did not succeed at the destination

And over on the hyper-v host you were trying to migrate the virtual machine onto you'll get the equally as amazing Microsoft-Windows-Hyper-V-High-Availability-Admin log entry of:

Source: Microsoft-Windows-Hyper-V-High-Availability
Event ID: 21111
Description:
Live migration of 'Virtual Machine <VM NAME>' failed.

Oh thanks, it didn't work because it failed.

Finally after reading many a technet article and support thread I stumbled onto the fix. It was simple. Here's the details for anyone else who suffers this problem:

  • On any node in your hyper-v cluster, open up Failover Cluster Manager

  • Select the cluster name

  • In the bottom right corner of the manager window, click Take Offline

  • Again in the bottom right corner, under More Actions, click Repair

  • This will bring the cluster back online and magically fix the mysterious problem causing live migrations of VMs to fail

Best of all, it will do this with out any disruptions to running VMs. Enjoy!