Вот, оригинальный текст так сказать:
The Resize-VHD cmdlet changes the maximum physical size of a virtual hard disk. It can expand both VHD and VHDX files but can shrink only VHDX files. The shrink operation fails if it would shrink the virtual disk to less than its minimum size (available through the VHDX object's MinimumSize property).
If the virtual disk file connects to a virtual machine's IDE chain, you cannot resize the virtual disk while the virtual machine is online. If the virtual disk file connects to a virtual machine's SCSI chain, you can resize the virtual disk while the virtual machine is online.