Note: Windows Server 2012R2 and 2016 are not affected by this and will always be keeping the Virtual Machine online during the backup operation.
The requirements for Hyper-V are listed below:
- The Guest must be running one of the supported OS's of the relevant Host OS as below:
- Host running Server 2008 R2 - https://technet.microsoft.com/en-US/library/cc794868(v=ws.10).aspx
- Host running Server 2012 - https://technet.microsoft.com/en-us/library/dn792028.aspx
- Host running Server 2012 R2 - https://technet.microsoft.com/en-us/library/dn792027.aspx
- Host running Server 2016 - https://technet.microsoft.com/en-gb/windows-server-docs/compute/hyper-v/supported-windows-guest-operating-systems-for-hyper-v-on-windows
- The latest "Integration Services" must be installed. This can be checked by connecting to the virtual machine and then go to 'Action' > 'Insert Integration Services Setup Disk'.
- In the Properties dialog of the VM, from either Hyper-V Manager or SCVMM, look on the Integration Services tab and ensure that “Backup (volume snapshot)” is checked (see screenshot below).
- The guest VM is in a running state
- All the guest VM's disks have ample free space available for the internal shadow copy to complete. You must have 10% free disk space on each disk.
- In the guest VM, the service with name "Hyper-V Volume Shadow Copy Requestor" is running
- The Snapshot File Location for the VM is set to be the same volume in the host operating system as the VHD files for the VM
- The guest operating system must have its own VSS support (Vista desktops and later, 2003 Server and later).
- The guest VM must have a SCSI controller attached in the VM settings (in Hyper-V Manager). There is no need to have any disks on the controller, but it must be present.
- The guest VM must not have any Shadow Storage assignment of a volume explicitly set to a different volume other than itself.
- There must not be any App-V drives installed on the virtual machine as this creates a non-NTFS volume.
- If the guest OS has a system reserved partition, verify that it has at least 45MB of free space. If less than that is free, ensure that a windows shadow copy can be created as per the screenshot below:
- All of the virtual machine’s volumes must be formatted with NTFS/ReFS. The volume that contains the .VHD(s) for the VM must also be formatted with NTFS/ReFS. The guest operating system’s disks must be “Basic”, not “Dynamic” (this is not the same as dynamic vs. fixed VHDs, see screenshot below).
- The “COM+ Event System”, “Distributed Transaction Coordinator”, “Remote Procedure Call (RPC)”, and “System Event Notification” services must be running within the VM. By default, these are set to “Automatic” and/or “Automatic (Delayed Start)”. The “COM+ System Application” and “Microsoft Software Shadow Copy Provider” and “Volume Shadow Copy” services must at least be set to Manual, which is the default for these. It is acceptable, but not required, to set them to “Automatic” or “Automatic (Delayed Start)”.
- Check if you are getting a "vmicvss" with event ID 13 inside the Application event log of the VM that is specifying that Windows cannot perform an online backup of this system. Event below:
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\
The simplistic explanation of these backup types is that the VSS writer is called within the Hyper-V host. It notifies the Integration Services within the VM that a backup is about to occur. Integration Services negotiates with the VM’s VSS writer to take the VSS snapshot. With the exception of the Integration Services, all the above requirements are generally the same for a VSS-based traditional backup; the difference is that all components of the VM must comply. For instance, a traditional backup on a system with a dynamic disk or FAT32 volume can use the VSS writer for everything except the protected data that lives on a dynamic disk or FAT32 volume. Because the entire VM must be synchronized with the parent partition’s VSS writer, the entire VM must be able to interact with VSS or the entire VM must be paused while the parent’s VSS writer operates on it.