“Each IDE controller can have two devices. You can not boot from a SCSI controller. This means an IDE disk will be required. The boot disk will be IDE controller 0 Device 0. If you want a CDROM it will consume an IDE device slot.” Source: MSDN Blog The hypervisor that runs the virtual BIOS does not support booting from a SCSI controller, today, but it does support the following boot devices: CD IDE Legacy Network Adapter Floppy The root reason is SCSI in a synthetic device and there is no VMBUS until after boot. One might think that this shouldn’t be a problem, after all, the virtual machines can still boot from regular IDE-based virtual disks. So where’s the catch? The main problem is related to the fact that in Virtual Server, virtual SCSI controllers have major performance benefits over virtual IDE controllers. In Virtual Server, it is recommended to attach the Virtual Disks to one or more SCSI controllers to improve disk input/output (I/O) performance. IDE is limited to
No matter how sophisticated the technology is , It still takes people !