Quickly Recovering Replication on Hyper-V

Two weeks ago, I had to recover from a sizable power outage. When this happened, my first priority was to make sure that all of my virtual machines were running well. Once I had done this, my next goal was to get Hyper-V Replica back up and running – so that I would be protected against any future problems.

Now, Hyper-V Replica would have eventually sorted itself out – but I did not want to wait for this to happen organically. I wanted things fixed immediately.

Hyper-V Replica had correctly detected that was a problem, and had scheduled resynchronization for all of my virtual machines. What I did to speed up the process was to shut down all non-critical virtual machines, and then use PowerShell to run the following command:

Get-VM -ComputerName Hyper-V-1, Hyper-V-2 | ?{$_.ReplicationMode -eq “Primary” -and $_.ReplicationHealth -eq “Critical”} | Resume-VMReplication -Resynchronize

This caused replica resynchronization to start immediately for all virtual machines that were reporting that replication was in a critical state. At this stage I must give a word of caution. You may be wandering why I shut down non-critical virtual machines before doing this. The reason is that initiating a mass resynchronization like this will generate a huge amount of disk activity, as Hyper-V goes through and rechecks all of the data on disk. I shut down non-critical systems to try and minimize the amount of data churn that occurred during this process.  Even with this precautionary step, I could feel the system slow down overall while resynchronization was happening.

But after a relatively short period of time, resynchronization was complete and my computers were (almost) back to normal.

Cheers,
Ben