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Title
Hyper-V Host Level Snapshots Fail with 'Microsoft Hyper-V VSS Writer' Error -
Description
When snapping a 2008 R2 Standard / Enterprise Hyper-V Server that has Guest VM VHD's on a protected disk the snapshot of the host will fail with the following: "Hyper-V Event Viewer Error"
HYPERV EVENTS / EVENT 10111, Hyper-V-VMMS
Failed to mount the virtual hard disk \\GLOBALROOT\Device\HardidskVolumeShadowCopy5\Data Virtual Hard_disk 4dfj68-3435n-df45kj6-8735798u7b.avhd for virtual machine "EAMSDBTEST" (Virtual machine ID 21135FJ6JG-0DFC4-34978-DRG-34658ES) .
Application EVENTS
The VSS writer 'Microsoft Hyper-V VSS Writer' failed during snapshot phase 'DoSnapshotSet' with error 2147754806. Writer state is WaitingForBackupComplete -
Cause
If there are Guest VM's running on the Hyper-V Host being backed up, when the snapshot runs the host must have the ability to auto-mount or you will receive Hyper-V and Application Event Errors
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Resolution
During an online backup Volume Shadow Copy Service (VSS) requires mounting the snapshotted VHDs in order to revert them back to their proper state. If automount is disabled, VSS cannot mount the snapshotted VHDs as required.
To determine if automount is enabled run DISKPART.EXE from a command prompt, and then run the following command at the DISKPART prompt:
automount
which shows that disks are not automounted
In elevated command prompt type:
MountVol /E
This may fix the issue so that server backup works successfully on the host machine.