Windows Server 2016 Support

The Virtual Server Agent for Microsoft Hyper-V can run on Windows Server 2016.

Windows Server 2016 hosts provide built-in support for the following functions:

  • Backups
  • Restores
  • Virtual machine filters
  • Disk filters
  • Native Microsoft changed block tracking
  • SMB shares, CSV storage, storage pools, and Storage Spaces Direct (hyper-converged storage that uses local storage from multiple Hyper-V hosts)
  • VM Lifecycle Management


  • For guest VMs running on Windows Server 2016, the Virtual Server Agent uses production checkpoints to perform application consistent backups, without requiring that production checkpoints are enabled on the virtual machine. The Virtual Server Agent also supports backups of virtual machines that run in a nested cluster.
  • For guest VMs running Windows 2008 R2 or earlier and for virtual machines that run in a nested cluster, the Virtual Server Agent uses standard checkpoints to perform crash consistent backups.
  • Windows Server 2016 uses binary configuration files for guest VMs (VMCX and VMRS files).
  • Windows Server 2016 includes enhanced support for the ReFS file system, which is optimized for virtualization. The support includes the ability to merge checkpoints that are used for backups.
  • Restores cannot modify configuration files directly. For restores, the Virtual Server Agent imports the virtual machine from the backup and modifies the VM configuration after importing the VM (for example, attaching restored disks and reconfiguring networks). This type of restore is also supported for Windows Server 2012 R2 nodes.

Changed Block Tracking

For Windows Server 2016 or later, Commvault CBT uses Microsoft's Resilient Change Tracking (RCT) feature to track changed blocks on the virtual disks.

For virtual machines running in a Windows Server 2016 Hyper-V cluster, the use of checkpoints for backups simplifies the backup process. For each virtual machine, the backup takes a checkpoint that includes only that virtual machine.  Once the backup is completed, the checkpoint is converted to a reference point with a unique ID and saved with the backup. Changed block tracking uses the reference point to identify changes since the last backup. The reference point is retained until the next backup is completed and a new checkpoint is generated.

Mixed Mode Clusters

In a mixed mode cluster where some nodes have not yet been upgraded from Windows Server 2012 R2 to Windows Server 2016, Windows Server 2016 operations are not supported until all nodes in the cluster are upgraded to 2016 and the functional level of the cluster is switched to Windows Server 2016 mode. Backups and restores use the same processes as Windows Server 2012 R2.

The behavior of changed block tracking varies in a mixed mode cluster:

  • If both the VSA proxy and the virtual machine proxy are running on a Windows Server 2012 R2 node, Commvault changed block tracking is used. Otherwise, incremental backups use the VSS backup method with CRC for changed block tracking.
  • If a virtual machine fails over from a Windows Server 2012 R2 node to a Windows Server 2016 node, incremental backups use the VSS backup method with CRC for changed block tracking. If the virtual machine fails back to a Windows Server 2012 R2 node, CBT resets and the next incremental backup includes all of the virtual machine data (equivalent to a full backup).

Virtual Machines Versions

In a new Windows Server 2016 cluster, virtual machines are version 8 or later.

In a cluster that has been upgraded to Windows Server 2016, virtual machines using older versions can still run, but cannot use all Windows Server 2016 host features. For example, all virtual machines running on a Windows Server 2016 node must be upgraded to version 8 or later before they can use Windows Server 2016 changed block tracking. In a Windows Server 2016 node that includes older version VMs, incremental backups include all of the virtual machine data (equivalent to a full backup).

Last modified: 12/5/2018 9:31:11 PM