Figure 2.5 Adding a SCSI controller to a generation 1 virtual machine
Each SCSI controller supports up to 64 hard drives attached, which equates to a
maximum of 256 disks attached via the SCSI bus. Like the IDE controller, those hard
disks can be virtual hard disks or mapped to physical hard disks on the host (pass-
through storage). The SCSI controller also supports the hot-add/hot-plug of disks to a
running virtual machine, which is a capability not available on the IDE controller. The
SCSI controller offers even more functionality in Windows Server 2012 R2:
Shared VHDX between multiple virtual machines
Dynamic resizing of VHDX filesAlways use SCSI-connected disks where possible in the virtual machine and restrict
use of IDE-connected disks to the operating system and DVD drive.
COM PORTS
Generation 1 virtual machines include two COM ports, COM 1 and COM 2, which can
be connected to a named pipe either local to the Hyper-V host or on a remote
computer. The use of COM ports is generally deprecated, and it is typically restricted
to certain types of guest kernel debug scenarios.
USB PORTS
If you are looking at a virtual machine settings dialog box, you may wonder where
USB devices are found. How do you map a USB device attached to the Hyper-V host
directly through to a virtual machine? You won’t find it, and the reality is you don’t
want to find it.
There are two scenarios for USB devices to be accessed in a virtual machine:
As part of a user’s session to a virtual machine
Always available to the virtual machine—for example, a USB dongle that must be
available for a piece of software or service to functionHyper-V does not allow the pass-through of a USB-attached device on a host to a
virtual machine. This would break the desired abstraction of the virtual machine from