While investigating a backup issue with some VMs I noticed an entry in the VEEAM Backup & Replication logs that the Hyper-V integration components were out of date.
This was the case on all the guests on that particular cluster actually. A quick look at the IC version on the host showed them to be at 6.3.9600.17831.
Comparing that to the ones in the guest made clear very quickly that those were at 6.3.9600.16384. So lower.
A web search for Hyper-V Integration components led us to KB3063283 “Update to improve the backup of Hyper-V Integration components in Hyper-V Server 2012 R2”on their Hyper-V hosts. They keep a tight ship but due to regulations they are normally 3 to 4 months behind in patches and updates. So in their case they only recently installed that update. KB3063283 Updates the Hyper-V Integration Components for Windows Server 2012 R2 to 6.3.9600.17831
So a little word of warning while you are keeping your Hyper-V environment up to date (you should), don’t forget to update the integration components of your virtual machines. A good backup product like Veeam Back & Replication will log this during backups. It might not make the backups fail per se but they have been updated for a good reason. This upgrade was even specifically for backup related issues so it’s wise to upgrade the virtual machines to this version a.s.a.p..