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.

Some facts:

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.

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