Hyper-V SnapShot Files – AVHD and VHD? What The ?

A couple of days ago I wrote about some issues I was having with one of my Hyper-V Virtual Machines and the snapshots that were associated with it causing my System Drive (C Drive) to run out of disk space. From what I was reading if you turn off the Virtual Machine in question a merging process will be conducted and the AVHD Files that are associated with the VHD File will merge together and form one file, a VHD one. This is what I was after.

I was reading and article by “The Virtual PC Guy’s” on Snapshotting under Hyper-V, and I determined that if I deleted the snapshots then the AVHD Files should be merged? But for some reason they did not merge?. Anyway the way to get these files merged to their parent VHD file (for me anyway) was to turn the VM off and just let the merge take place. Now I thought this process would take some time so I scheduled it for Friday night, my VM was a Microsoft Exchange Server, sureley no one would be checking their emails on a Friday Night !

I had 3 AVHD files that I wanted to get rid of, so I turned the VM Off and the “Merge in Progress” appeared in the Hyper-V Manager so I let it run it’s course. About 50 mins later the merge process was complete and 2 of the AVHD Files just VANISHED, great! but there was still one left? So I decided to turn the VM off again and what do you know another Merger was taking place, so again I left this happen and after it had completed the final AVHD File dissappeared and I was left with one VHD File, FANTASTIC!

One thing I learnt from this experience was that the VM writes to the AVHD Files and doesn’t appear to touch the VHD File (Parent File). I think I got myself into this situation because the Snap Shots were not deleted corectly. So now I am going to do some more testing on Hyper-V Snap Shotting and get a better understanding on how this works.

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4 thoughts on “Hyper-V SnapShot Files – AVHD and VHD? What The ?

  1. Jason

    I accidentally enabled snap shots in a vm and would like to get rid of the snap shot and merge it to the parent vhd. how exactly do i do the merge? i dont see the option at all in hypver v manager. I want to do this so I can get rid of all these .avhd files. please any help would be gladly appreciated jason888soul@gmaill.com

  2. Jim

    Does a merge actually replace the data in your current server? So if I allow a merge, will my server basically lose the current data and have the old data replace it?

  3. David

    What size did your exchange server get to with the snapshots? I’m going through the same thing with an exchange server, and scheduled a whole night of downtime. Hoping to get a decent estimate of how long I’ll be burning the midnight oil :)



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