Hyper-V Program Manager
There has been some confusion over when users should use SCSI or IDE virtual hard disk inside of their virtual machines. The first thing to note is that it does not matter what sort of physical hard disk you have in your computer when you are making this decision.
There are a number of factors to consider:
The final thing to consider is performance - and this is a bit tricky. Contrary to common sense, the performance of our emulated SCSI controller is slower than that of our emulated IDE controller. The reason for this is that the SCSI controller is a lot more complicated to emulate than the IDE controller. Now - this changes once you have Virtual Machine Additions installed. As part of Virtual Machine Additions we install an accelerated SCSI driver. Once this driver is installed the performance of our emulated SCSI controller is significantly faster than our emulated IDE controller.
So with all of this in mind, my recommendation is this: