There’s been plenty of blog posts out there saying that there is no support for SCSI in Hyper-V. That’s not true. What is true is this. You can use SCSI controllers for disks but not for your boot disk. Your boot disk must be on an IDE controller.
IDE: Hyper-V uses en emulated IDE controller. This means there is a little bit of overhead in processing disk operations. That’s not so bad for lightweight VM’s. You can have two IDE controllers, each with 2 devices. One of these is your virtual DVD drive which you should probably disconnect when you don’t need it.
SCSI: Hyper-V uses a SCSI controller that is not emulated. Instead it uses the virtual machine bus which is much faster and requires less CPU overhead.