One of the primary new features coming in Windows Server 2012 R2 Hyper-V is the introduction of what Microsoft is calling the Generation 2 Virtual Machine. These new VM types are very different from their predecessors in one critical way: They are designed to be virtual machines and only virtual machines. Whereas traditional virtual machines carry vestiges of their physical past, Generation 2 VMs shed these evolutionary anachronisms, bringing with them a number of benefits as well as a couple of challenges.
Evolution in action
BIOS has been around forever, but with Generation 2 VMs, BIOS has gone away in favor of the more flexible and more secure UEFI boot architecture, which also provides the ability to implement secure virtual machine booting.
In keeping with the all-virtual-all-the-time nature of these new virtual machines, Microsoft has stripped a number of emulated physical devices from Gen 2 VMs. Instead, there are software-based devices in their place. This reduced need to emulate physical hardware resources results in reduced overall resource need for the virtual machine.
As a part of this resource streamlining operation, Microsoft is also replacing the virtual IDE devices in Gen 2 VMs with virtual SCSI devices. This will enable such activities as using the new VHDX disk format for boot, which allows volumes of up to 64 TB in size as well as the ability to resize the volume while its online.
Microsoft claims that Gen 2 VMs can boot 20% faster than their older cousins and that administrators will enjoy 50% faster operating system installation times.
Challenges
Of course, every change brings with it come challenges. In humans, our changing diet has led to an appendix that no longer performs a critical function, but it can still rupture and poison the host. With Hyper-V, there are a couple of items that administrators need to consider before deploying Generation 2 virtual machines. First, only 64-bit operating systems, including Windows 8, Windows 8.1, Windows Server 2012, and Windows Server 2012 R2 and later operating systems are supported inside these native virtual constructs.