The Volume Shadow copy operation failed

When you try to make a Full Backup of your server using Windows Backup feature, you can get this error (See Figures below)

 

If your server runs Hyper-V with several VMs, these Virtual Machines could be the source of the problem. To check if this is the case, just open Event Viewer and go to :
Application and Services Logs -- Microsoft -- Windows -- Hyper-V-VMMS -- Admin,  then find the name of the VM or VMs which cause the problem.

After these steps, you have just to verify two things :
    - All Snapshots on this VM (or VMs) are merged.
    - There are enough free space on C:\ partition in each VM causing the problem.

How to get Hyper-V on Windows 8

Great New !! With Windows 8, you can use Hyper-V with all his features as they are on Windows Server 2012. So you can build your own test infrastructure on your Laptop or Desktop computer and why not, export and import your VMs from your computer to the server over Windows Server 2012.
There is no need to have a dual boot or a second machine built specialy for Hyper-V.

To install this feature, just go to : 
Control Panel -- Programs and Features -- Click "Turn Windows features on or off" -- Check "Hyper-V"