I look at Windows Server 2012 Hyper-V as a whole new generation of Hyper-V from
the previous versions. It took Hyper-V to new levels of scalability and functionality
and made it a true enterprise hypervisor, bringing in major new technologies such as
Hyper-V Replica, Network Virtualization, SMB 3 usage, and Live Migration. I look at
Windows Server 2012 R2 as the continued advancement of the Hyper-V technology,
refining many of the capabilities based on the feedback of enterprises that deployed
Windows Server 2012 Hyper-V. Many organizations will welcome the 2012 R2
enhancements.
No scalability changes were made in Windows Server 2012 R2. I think most people
would agree that the scalability of Windows Server 2012 meets today’s and
tomorrow’s requirements. The focus was on improving the utilization of
environments and fully embracing the technologies that companies were utilizing.
GENERATION 2 VIRTUAL MACHINE
The format of virtual machines has not really changed since the first version of Hyper-
V. Ten years ago, virtual machines required a lot of emulated hardware, because
operating systems didn’t natively understand virtualization. This is no longer true
today. Nearly all modern operating systems understand virtualization and the
synthetic types of resources available, making the emulated hardware previously
required for compatibility not required.
Windows Server 2012 R2 introduces a new type of virtual machine, a generation 2
virtual machine, which removes all of the legacy emulated hardware previously
present and shifts to a UEFI-based (User Extensible Firmware Interface) virtual
machine exclusively using synthetic SCSI (allowing virtual machines to now boot
from the synthetic SCSI) and network adapters (including PXE boot from a synthetic
network adapter). Generation 1 virtual machines are still available, and there is no real
performance improvement of a generation 1 vs. generation 2 virtual machine after the
OS is installed and running, but a generation 2 virtual machine will install and boot
faster.
STORAGE ENHANCEMENTS
One feature that did not make Windows Server 2012 Hyper-V was the capability to
dynamically resize a VHDX attached to a running machine. For some organizations,
just adding VHD/VHDX files to a running virtual machine was not sufficient. 2012 R2
Hyper-V supports the dynamic resizing of VHDX files attached to the virtual
machine’s SCSI controller. This dynamic resizing supports both increasing the size
and reducing the size, provided sufficient unpartitioned space exists within the VHDX
file.
VHDX files can be shared among multiple virtual machines in 2012 R2 Hyper-V; and
these shared VHDX files, which are hosted on Cluster Shared Volumes or a scale-out
file server, are seen to the virtual machines as shared SAS storage and can be used as
shared storage within the virtual machine for guest clustering scenarios. This removes