Hyper-V backups using Backup Exec 2012 fails to create snapshot indicating a disk signature collision.

Problem

When performing a backup of Hyper V virtual machines the backup jobs may fail while creating snapshots and indicating that disk signatures for vhd's are colliding.

Error Message

\\\Hyper-V?Virtual?Machine\machine-name>". Snapshot technology used: Microsoft Volume Shadow Copy Service (VSS).
A snapshot could not be created.  The most probable cause is a disk signature collision between two or more VHDs that are assigned to the virtual machine.
 
0xa0009650 - A snapshot could not be created.  The most probable cause is a disk signature collision between two or more VHDs that are assigned to the virtual machine.
Also seen error:
0xa0009651 - A snapshot could not be created.  The most probable cause is a disk signature collision between a VHD that is assigned to the virtual machine and physical disk mounted on the Hyper-v host. 

Cause

1. The disk signatures for the virtual machine's (vhd's) are colliding.
2. The Hyper-V writers on the host machine are failing during the backup process.
3. If the disk space of the VM doesn't have enough disk space.
4. Using multi path i/o configuration which creates two identical disks of which one is active and one is passive (seen by IBM but other vendor might have the same configuration).

Solution

1. Check and Fix the Disk Signature Conflict. 

       To check Disk Signature or ID use the Windows DISKPART utility commands "detail disk" and "uniqueid".

       http://technet.microsoft.com/en-us/library/cc770877(WS.10).aspx

       Refer to the following image. The "Disk Id" should be unique.

        Contact Microsoft Support for further assistance changing the Disk Signature.

2. Check the writer status on the Hyper V host machine.

         Reboot the server to check if the writers are stable, re run the backup job.

         If writers continue to fail, Contact Microsoft Technical Support to resolve the issue with the writers.

3. Clear up additional space on the VM if it's out of space. 

    4.      Install an additional IBM driver specific for multi path i/o configuration (for more detailed information where to find the driver please contact your vendor)