Hyper-V Backup doesn’t interrupt running virtual machines (anymore)

  • Article

Hyper-V has always provided the ability to backup all your virtual machines from the host operating system.  In order to provide a consistent backup of the virtual machine – Hyper-V has traditionally employed two approaches:

  1. If the guest operating system has the Hyper-V backup integration service installed and running: use VSS (for Windows) or file system freeze (for Linux) to create a data consistent backup of the running virtual machine.
  2. If the guest operating system does not have the Hyper-V backup integration service installed or running: put the virtual machine into a saved state, and perform a backup of the saved virtual machine.

This second approach has always been problematic – as it takes a running virtual machine offline for the backup process.  The good news is that this second approach has been drastically improved in Windows Server 2012 R2.  Now, rather putting the virtual machine into a saved state – we take a checkpoint of the virtual machine.  This checkpoint is backed up, and deleted after the operation is complete.

The net result of this is that no matter what the guest operating system, and no matter what the state of the integration services inside the guest operating system, Hyper-V will never interrupt a running virtual machine as part of backing it up (anymore).

Cheers,
Ben

Comments

  • Anonymous
    February 16, 2015
    Awesome! Is this feature also available in Windows 10 Tech Preview? The more I hear about Hyper-V, the more impressed I am.

  • Anonymous
    February 16, 2015
    Nice to see the change. Thank you for the heads up!

  • Anonymous
    February 17, 2015
    What kind of consistency you get then? Crash-, file- or application-consistency? Also any drawbacks regarding performance when the 'checkpoint' is taken/deleted? And finally what if the 'checkpoint' doesn't get deleted? Does the next backup manage it or fail miserably? Thanks, Didier

  • Anonymous
    February 18, 2015
    The comment has been removed

  • Anonymous
    February 19, 2015
    PiroNet: DPM seems to be able to handle subsequent backups when a backup checkpoint doesn't get deleted.  However, it won't attempt to delete that snapshot ever again.  We have had a few of these stuck checkpoints and the only way to delete them that we found was to do so from PowerShell with Remove-VMSnapshot -Force.  SCVMM is unable to see them at all and the Hyper-V MMC sees them, but doesn't give an option to delete them like it normally would. D van den Akker:  Our testing has shown that if a VM datasource is listed as offline in DPM, it will revert to using saved state for backups.  This has usually been caused by Hyper-V services (usually Volume Shadow Copy Requestor and/or Data Exchange) inside the VM being stopped or in some other way unresponsive.  A restart of the affected services has resolved the issue on the few VMs we had this issue with.

  • Anonymous
    February 19, 2015
    Hi Ben, Microsoft does not support checkpoints till Production checkpoints in vNext. How the backup process is using them in this case ?

  • Anonymous
    February 23, 2015
    Samir there is a difference between not supported and not recommended.

  • Anonymous
    February 23, 2015
    Samir - Christian is correct.  They have always been supported, but not recommended. Cheers, Ben

  • Anonymous
    April 28, 2015
    I can't backup linux guests with vhdxs store on mutiple volumes recently. I remember i can backup them when i setup those guests. These guests does not have the Hyper-V backup integration service installed or running. Maybe this is the reason I can't backup them?

  • Anonymous
    July 07, 2015
    Ben, Does this imply that a differencing avhdx (for 2012R2) would be created only if the guest does not support integration services (or if they are not installed) ? In other words , if the guest is a windows VM with correct integration services installed would a .avhdx be created for it when the backup is initiated from the hyper-V host ? what would be its use in this case? Earlier I went through the below blog post from you and you have not mentioned anything about avhdx file's involvement in the step 5a for the 2012R2 section. Hence the question. blogs.msdn.com/.../how-hyper-v-backup-got-better-in-2012-r2-but-now-requires-a-scsi-controller.aspx

  • Anonymous
    November 04, 2015
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  • Anonymous
    June 22, 2016
    Hi. Is there a way (registry key or something) to disable this behavior of taking a checkpoint when VSS cannot be used? Sometimes the backup fails for one or other VM and those VMs stay in a endless "Backing up..." status in Hyper-V Manager along with the AVHDX.