Changes

In a traditional computing model, a computer system typically runs a single operating system. For example, a desktop computer might run a copy of Windows XP or Windows Vista, while a server might run Linux or Windows Server 2008 instance.

The concept of virtualization, as it pertains to this book, involves the use of a variety of different technologies to allow multiple and potentially varied operating system instances to run concurrently on a single physical computer system, each sharing the physical resources of the host computer system (such as memory, network connectivity, CPU and storage). Within a virtualized infrastructure, a single physical computer server might, for example, run two instances of Windows Server 2008 and one instance of Linux. This, in effect, allows a single computer to provide an IT infrastructure that would ordinarily required three computer systems.

Virtualization has gain gained a considerable amount of coverage in the trade media in recent years. Given this sudden surge of attention it would be easy to make the assumption that the concept of virtualization is new. In fact, virtualization has been around in one form or another since it first introduced on IBM mainframe operating systems in the 1960s.