Note: Looking for VMware requirements? You can find them here.
VM Backup has the ability to coordinate with VSS to back up virtual machines without taking them offline or interrupting them - normally called 'live' or 'hot' backups. but there are several conditions that must be met for this to occur.
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 - see supported OS's
- Host running Server 2012 - see supported OS's
- Host running Server 2012 R2 - see supported OS's
- Host running Server 2016 - see supported OS's
- Host running Server 2019 - see supported OS's
- Host running Server 2022 - see supported OS's
- Host running Azure Stack HCI - see supported OS's
- 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 VHDX files for the VM
- The guest operating system must support VSS
- 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.
More information can be found here: http://www.altaro.com/hyper-v/requirements-for-live-backup-of-a-hyper-v-guest-vm-hyper-v-vss-writer/
Warning! 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