Saturday, 25 February 2012

An Introduction to Virtualization

An Introduction to Virtualization 

Virtualization is a concept in which more than one operating system shares the same set of related hardware. Typically we used to install a single Operating System into specific underlying hardware architecture and that architecture would become dedicated to that specific Operating System. In virtualization we share the same hardware architecture to a number of OS installations. Since these systems do not directly interact with the bare hardware, it is called virtual Operating Systems or Virtual Machines. These Virtual Machines are completely independent of each other Virtual Machines can be implemented by any one of below methods

1. Software-based Virtualization
2. Hardware-based Virtualization

Software Based Virtualization

In this method the underlying hardware is emulated by means of special purpose software. The software is capable of emulating the hardware for each of the virtual machines. The Operating System that incorporates platform for virtualization is called Base OS or Host OS and the virtualized machines are called Guest OS. This software is typically a part of the base operating system over which the guest OS are installed. Examples include VMware and KVM.

Software based virtualization are based on one of the two approaches

a. Para Virtualization
b. Full Virtualization

Para Virtualization

 Here the Host OS presents a software emulated interface to the Guest OS that is similar but not exactly identical to the underlying hardware. In this kind the Guest OS is aware of the fact that it is running under a Virtualized environment and there is a layer of hypervisor between the Guest and the Host machine. Such kind of virtualization generally doesn’t support all types of Guests or proprietary operating systems.

Full Virtualization

 In full virtualization, the hypervisor or the virtual machine monitor exists between the virtualized operating systems and the hardware. It is responsible for multiplexing the system resources to the Operating System Instances. This technique supports all types of Guest operating systems because it attempts to present a completely transparent platform to its Guest operating systems.

Hardware Based Virtualization

In hardware-based virtualization, the underlying hardware itself incorporates the architectural support that facilitates building a hypervisor and allows guest OSes to be run in isolation.

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