Terminology

Due to an overlap of terms and some misperceptions about the ways that the Hyper-V Server product is delivered, terminology is a common sticking point even for people who have been working with the technology for some time. The following table provides accurate but short definitions for the most commonly misunderstood terms in relation to Hyper-V Server and clusters. These definitions will be expanded upon in detail throughout the course of this book, so don't worry if they are confusing at first:

Term	Definition
Hypervisor	A hypervisor is an operating system that manages other operating systems. The primary responsibility of the typical operating system is to allocate and manage resources for applications. In the context of a hypervisor, "applications" are guest operating systems.
Microsoft Hyper-V Server	This is a full-featured hypervisor from Microsoft. Available as a standalone, no-charge product that includes a reduced-functionality image of Windows Server for the purpose of managing the hypervisor. It is also available as a role within Microsoft Windows Server.
Server Core	A specific installation method of Windows Server from version 2008 onward. This mode does not include a graphical interface. It is a fully licensed copy of Windows Server. Hyper-V is available as a role within Server Core.
Host	A physical computer with a hypervisor installed.
Guest	Another term for virtual machine, although it is commonly used to refer to the operating system within a virtual machine.
Management Operating System	The operating system that is allowed to control the hypervisor installation. In any Hyper-V Server installation, Hyper-V Server is always the hypervisor and Windows Server is always the management operating system. This is also sometimes called a parent partition or host operating system, although those terms are falling out of favor.
Cluster	In the context of Hyper-V Server, a cluster refers to hosts joined together using Microsoft Failover Clustering to provide Hyper-V Server services.
Node	A single physical computer that is a member of a cluster.
Live Migration	A Hyper-V-specific implementation of relocating a running virtual machine from one node to another without detectable downtime for the services on that virtual machine or external consumers of those services.
Quick Migration	A Hyper-V-specific implementation of relocating a virtual machine from one node to another. This method involves gracefully stopping the virtual machine in some fashion and starting it again at the destination.
Saved State	A condition in which a virtual machine's operations have been paused. The contents of its system memory are copied to a disk file and the virtual machine is placed in a non-running condition.

Note

The term Hyper-V Core and its variants should not be used. Hyper-V Server is one product and Server Core is a particular mode for the Windows Server product. Combining their labels leads to confusion and should be avoided.