hyper-v snapshot sizing

Question

_{Wednesday, February 2, 2011 4:00 PM}

im configuring hyper-v server which host 5 virtual machines.total capacity nearly 100tb.if i want to run snapshots how do i calculate capacity for the snapshots

samj

All replies (4)

_{Wednesday, February 2, 2011 5:23 PM ✅Answered}

Unless you fully understand how you are goiing to implement snapshots, it is difficult to anticipate.

There are two types: when the VM is running, when the VM is powered off.

When the VM is powered off you only need to worry about the virutal disk snapshot files.  When the VM is running you need to worry about the virtual disk snpashot files in addition to the saved runngin memory state.  Configuration and meta data is so small it is barely worth worrying about.

The saved memory state is easier to deal with as it is equal to the memory setting of the VM.  2Gb of RAM = a 2Gb saved state file.

The virtual disk snapshots files are a different story.  Each is a differencing disk, that means that each has a maximum size equal to the first VHD in the chain.  The amount of change that is written to disk between each snapshot is really what determins how large each will be.  The most conservative estimate is that each snapshot can equal its parent VHD is size.  So, if you have a VM with a 40Gb virtual disk a snapshot could take up an additional 40Gb of storage (unlikely, but it could happen).

http://itproctology.blogspot.com/2009/04/hyper-v-snapshots-are-tkaing-up-large.html

Brian Ehlert (hopefully you have found this useful) http://ITProctology.blogspot.com

_{Thursday, February 3, 2011 3:22 AM ✅Answered}

Hi,

If you want to perform some tests or install some updates due to the potential issue, you can take a snapshot before the operation. After the tests, it is recommend that you remove the snapshots because it will affect the performance of the VMs, especially in a production environment.

By the way, snapshot is not a backup method also, if you want to back up the VMs, please use a regular backup tools instead of snapshots.

Best Regards,

Vincent Hu

_{Wednesday, April 22, 2015 5:06 AM}

Hi,

Is there any Microsoft Article to refer about calculation of SnapShot Size.

_{Wednesday, April 22, 2015 1:03 PM}

No there is not, as it cannot be predicted.

A snapshot is not a copy - it is captured changes over time.

I don't know about you, but I cannot predict the on disk changes of my machine into the future.

All you know is that a snapshot has the potential of equaling the maximum size of the root VM.

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