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Backup Hyper-V

Hyper-V is Microsoft's virtualization host. It allows users to create, run, and manage virtual machines.

Overview

Hyper-V backups have the following properties:

  • Windows "Core" Servers running Hyper-V are not supported. 
  • Individual Virtual Machines may be selected for backup.
    • The virtual hard disk files (.vhd or .vhdx) and snapshot files (.avhd or .avhdx) will be backed up for any selected virtual machine.
  • The Initial Store (InitialStore.xml) may also be selected for backup.
    • By default, this file is found in %systemdrive%\ProgramData\Microsoft\Windows\Hyper-V\
  • VMs are backed up by one of two methods.
    • The "Child VM Snapshot" method uses the Volume Shadowcopy Service (VSS) inside a child VM. This allows the VM to be backed up without forcing it into a saved state.
      • This is the default backup method. If a Child VM Snapshot cannot be taken, a Saved State backup is taken instead.
      • Child VM Shapshot backups have additional requirements as outlined below.
    • The "Saved State" method briefly places each VM into a saved state so that a snapshot can be taken. Once the snapshot is taken, the VM is returned to its previous state. 
      • This method is used if the Child VM Snapshot method cannot be performed.
  • New VMs will be automatically detected and backed up if all VMs are selected selected for backup. 
  • VMs that are removed from Hyper-V will be automatically removed from the backup if all VMs are selected for backup. 
  • VMs are not automatically added or removed from the backup if individual VMs are selected. 

Backup Levels

Hyper-V backups are always Full backups. 

Special Options

The following special options are available for Hyper-V backups. 

Back up a running VM only if its hot backup can be performed is a special option designed to keep VMs running smoothly during backup.

If enabled, ZCB will skip backup of a running VM if a "Child VM Snapshot" backup cannot be performed.

Requirements

The following requirements must be met for Hyper-V backups to function.

  • The Hyper-V VSS Writer must be started.
  • Backups of Cluster Shared Volumes are not supported.
  • Restore of Hyper-V virtual machines and Host Configuration must be done to the same version of Windows as took the backup. 
    • For example, if the original Hyper-V backup was taken on Windows Server 2008 R2, the restore must be done to Windows Server 2008 R2.

Additional Requirements for Child VM Snapshot backups

The following requirements must be met for Child VM Snapshot backups to function.

  • Backup (volume snapshot) Integration Service must be installed and running in the child VM. 
    • The service name is "Hyper-V Volume Shadow Copy Requestor".
  • The child VM must be in the running state. VMs that are not running always use the Saved State backup method.
  • The Snapshot File Location for the VM must be located on the same volume in the host operating system as the VHD files. 
    • Example: If the VHD files are on C:\, the Snapshot File Location must be on C:\
  • All volumes in the child VM must be basic disks. Dynamic disks are not supported by the Child VM Snapshot method.
  • All disks in the child VM must use a file system that supports snapshots, such as NTFS or ReFS. 
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