Run out of space in merge huge AVHDX file. any idea what to do? RRS feed

  • Question

  • I Hope you will help me with a huge problem..

    The problem start in one of our VM in hyper V.

    I had a 2TB unallocated space in that machine (win server 16) it and I wanted to move this space to the host (win server 16). so from the host I run a powershell to shrink space of this VM. BUT.. I had checkpoint on this VM (!!)..

    So after the shrink process I couldn't power on that VM.

    This VM had a 16TB hard disk.. (and no backup)..

    In the end I had one VHD that was 30GB on AVHDX that have 500GB (this was the newest/latest checkpoint) and one more AVHDX with 15+TB..

    After a lot of error message (mismatch etc) I decided to start merging the two AVHDX to the parent VHD. the first AVHDX (the 500GB) merged fine. now I need to merge the 16 TB to the parent.

    before the second merge process I enter to the settings of that VM (in the host).. In the hard disk I saw that this VM is pointing to the first AVHDX (that is not exist because I did the first merge process with that file) so of course the VM didn't power on... I didn't wanted to point the hard disk to the second AVHDX (the 16 TB ) so because of that I started the second merge..

    In that server (host) I had 5.5 TB free so I started the merging process. Now I have 400GB so I paused the merging process. the VHD is something about 6.5TB and the AVHDX is still 16TB.

    How can I increase the C drive? If I add external 10TB USB drive. how can I increase C drive with that USB?

    What will happens if i'll cancel the merge processes now and change the AVHDX in settings of this VM manually?

    I so need to get to the files in that VM.. So Frustration...

    Sunday, August 11, 2019 4:42 AM

All replies

  • Hi,

    normally, if you manage to cancel a merge gracefully, you end up with a readable VHDX chain that just hasn't been completely merged. In your case, after so much tinkering, it's difficult to say what will hapen but since the merge appears to have started, chances are that nothing bad will.

    I would focus on cancelling the merge, getting that large USB drive, mounting the VHD on the host and copying the contents to the USB drive rather than on trying to start the VM.

    Evgenij Smirnov

    Sunday, August 11, 2019 8:08 AM
  • thanks for your quick reply. I'm trying to export the files from hyper-v management and encounter error messages.

    Can I just copy the files to the network location (another server), from that server (the new server) to import the files and just merged them there? after that i'll try to export the merged file to the first server?

    Sunday, August 11, 2019 12:46 PM
  • Yes, if you manage to keep the absolute paths the same; otherwise the AVHDX will lose its parent VHDX and you will have to repoint it by editing the header which is a nice exercise but not with disks as big.

    Evgenij Smirnov

    Sunday, August 11, 2019 1:13 PM
  • Ok, I'll copy the root folder from server 1 (current) to server 2 (new one with big storage). after the files are copied I'll suppose I'll need to import the VM in server 2 and then to merge the files. In the import I have 3 options :

    Register in place, restore or copy. after I read about the three I'l still don't know what to choose. any idea?

    Sunday, August 11, 2019 1:18 PM
  • Register in place is fine

    Evgenij Smirnov

    Sunday, August 11, 2019 1:25 PM
  • Thanks. I'll try!
    Sunday, August 11, 2019 1:36 PM
  • Hi ,

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    Monday, August 12, 2019 6:31 AM
  • Hi ,

    Just want to confirm the current situations.

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

    Best Regards,


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    Wednesday, August 14, 2019 1:58 AM