VHDX files can take up a lot of unnecessary disk-space, especially if the disk is used for a lot of writes. A dynamic vdisk expands, but does not automatically compacts again.
Sometimes it is necessary to first defragment the disk. I use PerfectDisk V14 for this, but there are a lot of defragmentation tools around that work just as well. After the VHDX is defragmented and optimized for shrinking, open a command prompt with administrator rights and start DiskPart:
Type the following commands:
- select vdisk file=”<path to the virtual disk>” (quotes are mandatory if there are spaces in the path)
- attach vdisk readonly
- compact vdisk
- detach vdisk
The disk will now have shrunk to the size that the data on the disk is using (if defragemented properly).