supports two IDE controllers, each supporting up to two disks for a maximum of four IDE disks per guest.
Hyper-V guests support up to four SCSI controllers, each supporting up to 64 disks for a total of up to 256 SCSI disks per guest.
Unlike Virtual Server 2005 R2, once the Hyper-V integration components are installed in a guest, there is no performance difference between IDE or SCSI connected virtual disks.
Utilize an IDE connected disk as the boot disk. Add an SCSI controller and SCSI connected disks for guest data volumes.
In Hyper-V R2, Guest Disks can be hot-added via the virtual SCSI controller. Therefore, consider pre-creating a SCSI controller device on all VMs for hot-add VHD capability.
Hyper-V can also utilize iSCSI storage by directly connecting to iSCSI LUNs utilizing the guest‘s virtual network interface cards (NICs). Guests cannot boot from iSCSI LUNs accessed through the virtual NICs without utilizing a third-party iSCSI initiator.
In this diagram, iSCSI storage is utilized. With iSCSI, a third access scenario is added, which is direct iSCSI access utilizing the network connectivity of the guest.
Do not confuse iSCSI LUNs presented to the host and then utilized by the guest with iSCSI LUNs presented directly to the guest. In the former, access to the iSCSI LUN is provided via the host‘s network connectivity. In the latter, access to the iSCSI LUN is provided via the guest‘s network