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Virtualization Basics: Types of Virtualization

written by: Ashwin Satyanarayana•edited by: Rebecca Scudder•updated: 8/19/2008

Virtualization is one those things every IT manager you know is talking about endlessly. The hype has a reason though. Before we plunge into the gory technical details, it is important to know what exists -- learn the different types of Virtualization. Then learn about Server Virtualization.

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    What do you get when you are able to do more with your computers, without having to invest in excess space, without buying more computers, and not spending an extra cent? You would do a lot more than ever before. Virtualization promises you this and more.

    Enhanced resources and computational prowess is brought about by virtualization because it separates the actual computing operations away from the hardware limitations we usually have. For example, if you were to store digital files on your hard-drive alone, you would be limited to a space as determined by the capacity of your hard drive -- but if you were go virtual, you suddenly have all the space in the world ( at least it appears that way).

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    Illustration of How Virtualization works

    How Virtualization works
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    Types of Virtualization

    Broadly speaking, there are two common types of virtualization -- storage virtualization and server virtualization. Server virtualization and storage virtualization are further divided into many “sub-types,” depending on how you look at it. Here we discuss server virtualization.

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    Server Virtualization

    Server virtualization is what you generally see used with data centers, web hosting companies and many other small and medium businesses.

    Operation System Virtualization: This sort of virtualization mainly uses a “container” approach wherein virtualized clients (which have applications running in them) interact with a well-known and common operation system. As an example, think of a web-hosting company which offers a “Shared Hosting” package. They usually make you feel as if they have a server that hosts your website and appear as if this server just manages your website and nothing else. However, the truth is that this very server also manages to host many other sites as well. This form of virtualization comes in handy with multiple clients (computers) that use the same applications and use the same operation systems.

    Hardware Emulation : As the name suggests, hardware emulation is all about using standard virtualization software (also called a Hyper Visor) to form a emulated hardware environment (Called VMM -- Virtual Machine Monitor), for guest operating systems to function on. The way this differs from an operating system virtualization is that you have guest operating systems (Windows, Mac or Linux) machines interacting with a VMM individually as a consistent package -- making it one unit, virtually. This package can be cancelled, shut down when not required or even migrated. The VMM in turn interacts and resides on the Hyper Visor (Software like VM Server, etc.). This kind of system allows for use of various operating systems and different computing systems for each one of the virtual machines, unlike the operating system virtualization which has severe limitations to variety.

    Para virtualization: Para Virtualization is the much sobered down, budget-minded virtual traffic police cop. Instead of having anything to with code-heavy software like the Hyper Visor (the virtualization software) or just emulating hardware as in hardware emulation, we now have a wafer-thin code and a relatively light software program which just allocates resources to the requesting guest operating system. Much like a traffic cop, it allocates the limited hardware resources --like server space -- to the guest operating systems which are needed at that point and limits access from non-active guest operating systems, thereby saving resources.

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    More Examples of Virtualization