18-03-2011, 04:52 PM
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ABSTRACT
Virtualization is a proven software technology that is rapidly transforming the IT landscape and fundamentally changing the way that people compute. Today’s powerful x86 computer hardware was designed to run a single operating system and a single application. This leaves most machines vastly underutilized. Virtualization lets you run multiple virtual machines on a single physical machine, sharing the resources of that single computer across multiple environments. Different virtual machines can run different operating systems and multiple applications on the same physical computer.
We use a desktop which runs on a single operating system. We also see systems which have more than one operating system installed, but run on one via dual boot. The utilization percentage of these systems is much low when compared to the level of their capability.
By virtualization we can run simultaneously more than one operating system on the physical machine. The main idea behind this is to better utilize the available resources in an organization.
INTRODUCTION
WHAT IS VIRTUALIZATION?
We are familiar with the concept of multiple processes running simultaneously and sharing the resources of a single computer. This is achieved by operating system acting as a single point of contact interfacing with the hardware resources, and there by controlling the access to hardware resources by multiple processes.
Virtualization can be thought of as an extension of this concept, where in multiple operating systems are allowed to share the hardware simultaneously by means of virtualization software.
An OS directly interacts with hardware in normal non-virtualized case. Now if we want to run multiple operating systems simultaneously, we need to have an abstraction layer between the OS and the actual hardware. This hardware abstraction layer fools the operating system into thinking that it is directly interacting with the hardware.
It is the one which enables the user to run more one than operating system simultaneously. On machines with single operating system the resources of that machine are set under that OS.
Here in case of virtualization there is a hardware abstraction layer called hypervisor or virtual machine monitor between the hardware and the operating system. With the help of this virtual machine monitor we can install and run more than on operating system. This hardware abstraction layer creates an illusion that each of the OS running is having its own resources, but actually they are sharing the same resources.
There are two types of virtualization
1. PARA VIRTUALISATION
2. FULL VIRTUALIZATION
1.PARA VIRTUALISATION :
Here the virtualization provides an abstraction, which is very similar, but not completely identical to the underlying hardware. Xen Virtual Machine and VMware ESX server are examples of this technique. Instead of completely emulating the underlying hardware architecture by the virtualization software, the virtualized guests collaborate with the hypervisor to achieve optimal performance. Para virtualization offers significantly improved performance; however, it requires modification to guest operating system. The guest OS is modified at low time to include Para Virtualization extensions. Hence it requires cooperation from the OS vendor.
Ex: sun xVM virtual box
2.FULL VIRTUALIZATION:
Here the virtualization software provides a complete emulation of the underlying hardware. All software that can run on the underlying hardware can run as is, on the virtual machine. The operating system does not need any modifications to be run as a guest OS instance. The guest OS instance can be any operating system supported by the underlying hardware.
Ex: VMware workstations, Virtual PC, QEMU.
With virtualization we can be
a) able to dynamically move resources
b) able to share resources
c) making better use of the resources
d) driving up utilization
After installing and running sun xVM virtual box it looks like this
