In the "old times" it was not recommended to use dynamic expanding disks in hyper-v. This create the issue of using very much disk space on the hyper-v host. (because we need allocate the space for the virtual disks)

I cannot find too much information about what is recommended today for windows server 2019.

What is recommended in 2021? Fixed disk size or dynamic expanding?

Extra information: The virtual server does not handle any big files. Only work with small size files (few kb, but many hundre thousands of them) if there is really no good reason for choosing fixed size, i want to convert all disks to dynamix expanding disks.

1 Answer 1


The main problems with dynamically expanding disks are fragmentation and overcommitment.

Fragmentation is really not an issue anymore with modern storage, especially SSDs which don't care at all where data is physically located; unless you are storing your VHDs on local mechanical disks, this should not be a concern.

Overcommitment can still be a problem, though; if a volume gets accidentally filled up and doesn't have enough free space when a dynamic VHD needs to expand, the VHD will get damaged and the associated VM will likely crash, possibly along with other ones stored on the same volume.

  • thank you. Part of the upgrade is to go from spinning disks to ssd, so then it will be dynamically disks. Then its enough to monitor the disks on the hyper-v host
    – SmallDev
    Sep 1, 2021 at 10:18

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .