How to enable Windows Server Backup support for the Hyper-V VSS Writer ?
In order to enable VSS based backups of Hyper-V VMs using Windows Server Backup you must add the following registry keys to register the Hyper-V VSS Writer with Windows Server Backup, Note that the WindowsServerBackup key is not created when installing. This key must be created manually. HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT \CurrentVersion\WindowsServerBackup\Application