Problem:  

Windows Server Backup fails on Windows 2012 R2 Hyper-v server.  System fails to create shadow copy.

Specific Windows Server Backup Errors:

-Backup not started.
-The backup operation of the volume did not start.
-Location is Invalid

Event Log Errors:

-The backup operation attempted at xxxx has failed to start, error code '0x8078000C' ('The specified backup storage location is invalid.').

-The backup operation that started at xxxx  has failed because the Volume Shadow Copy Service operation to create a shadow copy of the volumes being backed up failed with following error code '0x80780119'.

Background:  

The EFI-based server uses a GUID partition table (GPT) file system.  A GPT drive includes the following partitions:

• EFI System Partition:
  -The server boots to the EFI partition.
  -The EFI partition cannot store user data.
  -The typical size for a 512-byte sector drive is 100MB.
   
• Microsoft Reserved Partition (MSR):
  -Windows uses the MSR (i.e., recovery partition) partition to store security and recovery tools (e.g., Windows Recovery (RE).
  -The MSR cannot store user data.
  -The typical size for a the MSR partition is 300MB.  

Solution:  System partitions must have enough free space to create shadow copies of the partition -including both the EFI and MSR volumes:

• Partitions smaller than 500 MB require at least 50 MB of free space.
• Partitions larger than 500 MB require at least 320 MB of free space.
• Partitions larger than 1 GB require at least 1 GB of free space.

https://technet.microsoft.com/en-us/library/dd799232%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396
http://answers.microsoft.com/en-us/windows/forum/windows_8-performance/backup-error-0x80780119/78adc0e0-c793-4b6c-95db-af625f3c9fe7

DPM Hyper-V Network Administration