The Windows Core team posted a blog about how to add a pass through disk to a Hyper-V VM or child partition. Pass through disks are the fastest storage option for VM’s. Instead of using a VHD file, they are presented with a raw and unformatted volume. This is dedicated to the VM. The VM will then format the volume. You’ll use this option when you need VM’s running things like Exchange or SQL that need the very best in disk performance. Note that Fixed VHD’s get within 6% of the underlying disk speed.