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HyperV: application consistent RRS feed

  • Question

  • Hi,

    Are Snapshots created using WMI (createsnapshot() of Msvm_VirtualSystemSnapshotService ), an application-consistent copy ?

    Thanks

    Thursday, January 21, 2016 9:36 AM

Answers

All replies

  • Hyper-V Snapshots have changed over time.

    Are they application consistent?  In Server 2016, yes.  That term is used because by default the running memory state is not saved.

    Is a snapshot of a running machine (with a saved memory state) application consistent?  Technically no.


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.

    Thursday, January 21, 2016 3:33 PM
    Moderator
  • Thanks Brian. But how to get the application consistent backup in Win server 2012 using WMI.?

    Appreciate your help.

    Thursday, January 21, 2016 5:17 PM
  • Ah.  Now we are into semantics.

    There are Hyper-V Checkpoints / Snapshots.

    There are VSS Checkpoints / Snapshots.

    A backup provider should be hooking VSS, not using the Hyper-V Checkpoint process.  Or taking a Hyper-V Checkpoint to set a moment in time, backup the root virtual disk while the VM continues to run on the checkpoint and then remove the checkpoint.

    If you want application consistency guaranteed, you need to use the built in backup provider.  Not roll your own process.

    Hyper-V has VSS integration from the Host into the VM, then it is up to the application to be VSS aware.


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.

    Thursday, January 21, 2016 5:24 PM
    Moderator
  • I got your point. If using the HyperV WMI provider to create the snapshot, does this hyper-v checkpoint/snapshot process invokes VSS on VM to create an application consistency. Yeah, in 2016, there is parameter "application-consistent" passed to createsnapshot() but I don't see in Windows 2012.

    ==

    Or taking a Hyper-V Checkpoint to set a moment in time, backup the root virtual disk while the VM continues to run on the checkpoint and then remove the checkpoint.

    == 

    The plan is to follow the above process but does this give me an application-consistency ?? 

    Thursday, January 21, 2016 5:55 PM
  • That is a new option in Server 2016.

    Prior, you had to do it through VSS not through the Hyper-V checkpoint mechanism.

    Look at the history diagram here: https://github.com/Microsoft/Virtualization-Documentation/pull/118


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.

    • Marked as answer by Bala_T Friday, January 22, 2016 11:03 AM
    Thursday, January 21, 2016 6:49 PM
    Moderator
  • Thanks Brian for this document.
    Friday, January 22, 2016 11:04 AM