History of Hyper-V
So far in this chapter, I have not used the word Hyper-V very much. I have focused on
the challenges of traditional datacenters and the benefits of virtualization. I now want
to start looking at the changes to the various versions of Hyper-V at a high level since
its introduction. This is important because it will not only enable you to understand
the features available in your Hyper-V deployments if you are not yet running
Windows Server 2016 Hyper-V, but also show the great advancements made with each
new version. All of the features I talk about are covered in further detail throughout
this book, so don’t worry if the following discussion isn’t detailed enough. I provide a
high-level explanation of what they are in this part of the chapter.
I’ll start with the first version of Hyper-V, which was introduced as an add-on after the
Windows Server 2008 release. Hyper-V was not an update to Microsoft Virtual Server,
which was a virtualization solution Microsoft acquired as part of the Connectix
acquisition. Microsoft Virtual Server was not well adopted in many organizations as a
virtualization solution because it was a type 2 hypervisor, whereas Hyper-V is a type 1
hypervisor. There are numerous definitions, but I think of them quite simply as
follows:
Type 2 Hypervisors A type 2 hypervisor runs on a host operating system. The host
operating system manages the underlying hardware; the type 2 hypervisor makes
requests to the host operating system for resources and to perform actions. Because a
type 2 hypervisor runs on top of a host OS, access to all of the processor rings of
operating systems running in the virtual machine is limited, which generally means
slower performance and less capability.
Type 1 Hypervisors A type 1 hypervisor runs directly on the bare metal of the server
and directly controls and allocates resources to virtual machines. Many type 1
hypervisors take advantage of a Ring –1, which is present on processors that support
hardware virtualization to run the hypervisor itself. This then allows virtual machines
still to be able to access Ring 0 (kernel mode) of the processor directly for their
computations, giving the best performance while still allowing the hypervisor
management of the resource. All modern datacenter hypervisors are type 1
hypervisors.
It is important at this stage to realize that Hyper-V is absolutely a type 1 hypervisor.
Often people think that Hyper-V is a type 2 hypervisor because of the sequence of
actions for installation:
1 . Install Windows Server on the physical host.
2 . Enable the Hyper-V role.
3 . Configure and manage virtual machines through the Windows Server instance
installed on the physical host.