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Merging snapshots. RRS feed

  • Question

  • I have a question i couldn't find answer. So I have a virtual machines with vhdx and 2 avhdx drives. VHDX max size 500GB.

    All those 3 files were on 1TB storage. Both AVHDX increased to that level that no room left on 1Tb storage. So i cant merge them as well. I have attached 4Tb storage and moved VM storage via VM settings to new storage. So now i have tons of space to merge differentials to its parents. But one thing gives me worries.

    Main parent is something like (1)-362Gb its child is (2)-235Gb and its child (3) is 457Gb.

    I have to start merging 3 back to 2 so its mean 457 to 235 and i afraid that is will make more then 500 what is the limit and a it will fail destroying data. Could someone with more experience to bring in some light?

    By the way if its safe to merge can I do it while VM is online?


    • Edited by a.k.admin Tuesday, October 15, 2019 1:58 PM
    Tuesday, October 15, 2019 1:57 PM

All replies

  • The ability to merge snapshots online came in Hyper-V 2012.  You don't mention the version of Hyper-V you are running, but since you mention VHDX and AVHDX files, it appears that you are running at least that, so you should be able to merge online.

    You are not merging the AVHDX file to the other AVHDX file.  You are merging the AVHDX files into the VHDX file.  And the resultant file is not a sum of the individual file.  The AVHDX file contains changes to the VHDX.  That means that a block in the VHDX file on which data was changed will be replaced, not added, when the AVHDX file is merged.  Yes, added data in the AVHDX file will be added to the VHDX file, but that is generally a fraction of what is changed.  I am not aware of any limits other than enough storage to handle the merge.

    Obviously, you should have backup before you start in case anything happens.  It looks like you have enough room to handle the merge, but a backup is insurance.


    tim

    Tuesday, October 15, 2019 3:44 PM
  • Hi,

    Thank you for posting in forum!

    Yes, as Tim said, the data in the avhdx file is added to the vhdx file, but this is usually only a small part of the change. So I think we can merger them safely. If you still have concerns, backing up virtual machines is a good idea.

    >> By the way if its safe to merge can I do it while VM is online?

    Windows provide online merging snapshots function in Windows 2012 and later versions.

    This link presents the steps to merge the snapshots manually and may be helpful.

    Reference: https://social.technet.microsoft.com/wiki/contents/articles/6257.manually-merge-avhd-to-vhd-in-hyper-v.aspx

    Hope this can help you.

    Best Regards,

    Lily Yang


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    Wednesday, October 16, 2019 8:16 AM
  • Hi,

     

    Just want to confirm the current situations.

     

    Please feel free to let us know if you need further assistance.

     

                       

    Best Regards,

    Lily


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    Friday, October 18, 2019 3:13 AM
  • Hi,

     

    Was your issue resolved?

     

    If you resolved it using our solution, please "mark it as answer" to help other community members find the helpful reply quickly.

    If you resolve it using your own solution, please share your experience and solution here. It will be very beneficial for other community members who have similar questions.

    If no, please reply and tell us the current situation in order to provide further help.

     

    Best Regards,

    Lily


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    Monday, October 21, 2019 6:42 AM