Home > Virtualization Basics > Glossary of Virtualization Terminology

Glossary of Virtualization Terminology

To Understand Virtualization and its associated  concepts better , I always have believed that one must first  understand various terms that are associated with it . In this blog , I have tried to put across various terminologies that are associated with Virtualization .  This is a collection of terms that I learnt in my early days as a VMware Administrator from various VMware Community Links and Xtravit  Team Blogs .

Virtualization & Types :

Virtualization
The employment of technologies that allows multiple instances of an operating system to run concurrently (each in the context of a Virtual Machine) on a single machine, with its computing resources being shared between them. In a virtualization solution, the Guest Operating System can be completely different to the operating system on the underlying machine.

Server Virtualization
The virtualization of server workloads.

Application Virtualization
Application virtualization encapsulates applications from the host operating system and run them as if they are installed where in actuality they aren’t. This provides a number of benefits such as software portability, improved management as applications are centralized, and isolation which reduces application conflicts, eg: running different versions of the same application on the same computer.

Desktop Virtualization
The Virtualization of desktop workloads. Where the desktop runs is separated from where the desktop is used, maximizing flexibility, mobility and security. The virtualized desktop is provisioned in the datacenter and can be accessed remotely from a variety of client devices.

Virtualization related Hardware Technology Terms :

AMD-V
AMD’s implementation of Hardware Assist, originally codenamed “Pacifica”. The primary feature of these CPU extensions is to improve performance of Virtual Machine by removing the need for emulation through the hypervisor.

Intel VT
Intel’s implementation of Hardware Assist, originally codenamed Vanderpool. The primary feature of these CPU extensions is to improve performance of Virtual Machines by removing the need for emulation through the hypervisor

Hardware Assist
Specialized host processor, chipset and BIOS features that aim to improve the performance of the virtualization software running on it. Its “trap and emulate” mode of operation is similar to that used by Binary Translation. Examples are Intel’s VT and AMD’s AMD-V.

Binary Translation
A technique where non-virtualizable Guest Operating System instructions are trapped and translated into a series of simpler instructions before being submitted to the host CPU for execution, allowing the Guest OS to run correctly in a Virtual Machine without any modification. This is an alternative approach to Paravirtualization.

GeneralVirtualization Terms :

Hypervisor
Software that enables the running of multiple Virtual Machines on a single physical computer and that manages the sharing of the computing resources between them.

Bare Metal Hypervisor
A Hypervisor that runs directly on a host, eg: VMware ESX Server, Citrix XenServer, Microsoft Hyper-V Server and Oracle Virtual Iron. Also known as a “Type 1” or “Native” Hypervisor.

Paravirtualization
A virtualization technique involving the modification of an Operating System through the removal of non-virtualizable instructions in an effort to improve performance when running in a Virtual Machine. An alternative approach to Binary Translation and the opposite of Full Virtualization.

Host
The physical machine on which the Hypervisor and the Virtual Machines run on.

Host Operating System
The base operating system installed on a physical machine which interacts with the underlying hardware and, on top of which, Guest Operating Systems are installed in Virtual Machines. In a virtualization context, the Host Operating System is a Hypervisor.

Virtual Machine
A software implementation of a computer that acts and can be used just like physical computer.

Virtual Machine Monitor
The component of a hypervisor that implements the abstraction of the host hardware and manages the operation of a Virtual Machine and the Guest Operating System running in it.

Guest Operating System
The Operating System installed in a Virtual Machine.

Snapshot
The capture of the state of a Virtual Machine at a specific point in time, including all the Guest Operating System data and the Virtual Machine configuration, which can be returned to in the future, discarding any changes made since it was taken. A Snapshot typically provides Crash Consistent data.

OVF (Open Virtualization Format)
A vendor-neutral packaging standard that allows a Virtual Machine to be run on any hypervisor. It is a platform independent, efficient, extensible, and open specification for the packaging and distribution of virtual appliances composed of one or more virtual machines.

Virtual Appliance
A pre-defined, ready-to-run Guest Operating System and Application combination packaged and distributed as a Virtual Machine

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