I was having the same problem with these .avhdx files remaining after the backup checkpoints were removed. This started happening after running Windows Updates on the hosts on May 25, 2018 (bringing them up to kb4103723
). Same symptoms as described previously: there are no checkpoints listed but there are .avhdx files sitting in the Virtual Hard Disks folder for the machine.
I would have to shutdown the virtual machine, manually merge each of the .avhdx file into its parent, and then re-attach the original .vhdx and restart the machine. The guests affected were running any of CentOS 6, CentOS 7, Server 2008 R2, and Server 2016. One thing that was strange, is that it always seemed to be the same guests
with the leftover .avhdx files.
I finally stumbled upon kb4103720
which is not
coming down through WSUS. I downloaded it manually from the Update Catalog
as described in the article and installed it manually on each of my Hyper-V hosts yesterday, before my backups started for the night. This SEEMS
to have resolved the issue as of this morning. There are no .avhdx files to be found on any of my machines.
What's strange, is that KB article doesn't specifically
mention this issue in its release notes. The closest it comes is this:
- Addresses an issue that makes it impossible to revert to a virtual machine checkpoint. Reapplying the checkpoint fails with an error.
We don't use Veeam Backup for Hyper-V
so I can confirm that is not what's causing the issue. (We do use Veeam Backup for Office 365
.) We are (unfortunately)
using NetVault Backup
for a while longer until we can get off some legacy systems that Veeam does not support. For me, this issue seems to be related specifically to the update kb4103723
for Windows Server 2016. However, others seem to have been having this issue since before that update was released.
I'll keep a close eye on this and report back if the situation changes. For now I'm considering this resolved on my Hyper-V hosts.