I’m running Server 2012 Essentials running in a Hyper-V machine under Windows Server 2008 R2.
The Hyper-V host does a daily Windows backup at 9pm. The backup is configured to capture Bare Metal Recovery, System State, System Reserved, and the C: drive. It does not back up the E: drive where the VHDs of the client machines are stored. (The guest machines do their own backups.)
During the Hyper-V host backup, the following message appears five times in the Application log of the Server 2012 guest.
Log Name: Application
Source: vmicvss
Date: 11/29/2012 9:00:05 PM
Event ID: 13
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: SVR2012E.mydomain.local
Description:
Windows cannot perform an online backup of this system because scoped snapshots are enabled. To resolve this, disable scoped snapshots by creating the following registry value on this computer:
PATH: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\
CurrentVersion\SystemRestore\
DWORD: ScopeSnapshots
Value: 0
Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on the computer.
The Solution
In the Server 2012 Hyper-V guest, add the registry value as specified in the error message.
The Explanation
I asked in a Microsoft Partner forum about what scoped snapshots are and what this error means. Their answer:
I’ve confirmed with product team, this is an expected behavior. Scope snapshot is a special volume snapshot for volsnap performance. Mainly used by Windows critical updates. Scope means the volsnap only creates Copy on Write (Shadow) volume for the files that are involved in the updates instead of all the files on the volume.
Scope snapshot prevents volume snap revert operations, thus it will cause Hyper-V host backup failure since Hyper-V needs to perform mount and revert VM vhd operations on Hyper-V host. It can cause the hyper-v host backup failed even you didn’t include the hyper-v guest. That is the reason that we blocked it inside of VM during the backup.
Windows 8 Too
I just installed Windows 8 Pro as a guest on the same Hyper-V server and started getting the same message. In this case, the Server 2012 Essentials machine is successfully backing up the Windows 8 machine. I assume that setting the registry value will fix it there too.