VHD detaching and 137 & 14 errors

Question

I have a Hyper-V server running 2012. It has 4 VMs all running 2012. The host has a removable cartridge drive which contains a VHD for each VM which is attached within each VM as a drive used by Windows Server Backup.
The problem is that sometimes, but not often, the VHD will become detached and so the backup fails. The VMs are not rebooting (which would require reattaching the VHD) so that's not the cause.
I've looked in the event log and the only errors other than the failed backup are in the System Log. Event 137 from ntfs which says "the default transaction resource manager on volume <volumeID> encountered a non-retryable error and could not
start"; and Event 14 from volsnap which says "the shadow copies of volume <volumeID> were aborted because of an IO failure on volume <volumeID>".
I tend to think the errors came after the VHDs were no longer available, but I can't be certain.
I have the same setup at other locations and they don't have this problem of the VHD randomly detaching.
Anyone run into this before and know how to fix it?
Jonathan

Answer 1

Hi Jonathan,
The VHD is connect through Hyper-V settings or other methods such as iSCSI?
If it is in Hyper-V settings, you may also need to check the host server and see if any reconnected occurs between the host and the removable cartridge. 
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The VHD is attached by using the Attach VHD menu command in Desk Management in the VM and using a UNC path. This is how we do it on all our clients with an RDX cartridge drive containing VHDs that are used by all VMs for backup drives.
As I said, this is the only client this happens to and it's very random and never do all the VHDs become detached at the same time. It's usually one or maybe two of the 4 VMs that have this happen at the same time. I believe one time 3 of the 4 had it happen.
So I don't think there would be any reconnect errors between the host and cartridge as if there were, then all VMs would experience the problem at the same time.
Jonathan