Virtualization is the concept of decoupling the hardware from the operating systems and applications. This can be implemented a number of ways as we will discuss, but fundamentally it is achieved by inserting a layer between the server hardware and software components, to provide either the necessary interfaces, or a simulation of one component to the other.

"Server virtualization has quickly surpassed other forms of infrastructure virtualization, including techniques for virtualizing storage and networks. Globally, 75% of 1,221 enterprises surveyed by Forrester say they are aware of server virtualization technologies, 26% have implemented it, and 8% more will pilot it by the summer of 2007. The rapid adoption of server virtualization can be attributed to its near- and long-term advantages, which allow firms to reduce costs while making their infrastructures more flexible over time." (Forrester Research, February 7, 2007)