I was recently working with a Hyper-V VM that had a large branch of snapshots that I wanted to clean up, in order to conserve disk space. This was a SharePoint 2010 development VM which I’d configured specifically for a project, so I didn’t need all of the earlier snapshots. The environment has two VMs (one domain controller, everything else on the other), so I deleted all of the snapshots that I needed to get rid of on the first VM, one-by-one. From previous experience I knew that I could delete multiple snapshots before the initial merge operation completed. Hyper-V creates a queue of the merge operations that need to complete before the virtual machine can be restarted again. I left myself with only the latest snapshot and moved on to the second virtual machine to do the same. At this point I got a little too clever and started deleting the second snapshot before the first snapshot deletion was queued. It usually only takes a few seconds to complete but I jumped the gun and Hyper-V Manager threw two errors (4096 and 16410) regarding Virtual Machine file access when I tried to delete the second snapshot.
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