Deactivate scoped snapshots for Hyper-V virtual machines.
- You create an agentless (with Agent for Hyper-V on the host) backup of a virtual machine.
- Backup is performed offline (for more information see Microsoft Technet: Understanding online and offline backups). As a result, after backup start the virtual machine is not available for several minutes as it turns into Saved State.
- Backup runs and finishes successfully.
There are two possible causes for this issue:
- Backup (volume checkpoint) option is disabled. See Solution 1.
- VSS Snapshots in the guest OS are set to use scope snapshots. See Solution 2.
As a result, only particular files are included into Copy on Write (Shadow) snapshot, and not all the volume files. Scope snapshot are mainly used by Windows critical updates. You can see the following error message in the Windows Application Event Log of the virtual machine:
Event ID: 13
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\
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.
In the VM settings, check Backup (volume checkpoint):
Following the instructions in the error message, deactivate scoped snapshots:
- Open Windows Registry: Start -> Run -> regedit.exe
- Create a DWORD ScopeSnapshots parameter with Value "0" in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore\
If these solutions did not resolve the issue, check snapshot creation using Diskshadow. If the machine goes offline while creating a snapshot using Diskshadow, the problem is not specific to Acronis Backup and needs to be investigated by Microsoft support.
Please contact Acronis Customer Central if you need assistance.