Two years ago, if you asked about virtualization most people would respond with some comment about VMware, possibly Microsoft Virtual Server (which was in beta at the time) and if you were really lucky may have mentioned one or two other packages.

Today, virtualization is a byword for gaining greater efficiency and effectiveness from your hardware and there are many technologies vying for our attention.

Originally virtualization was a software technology, usually an application built on top of an existing operating system that could then be used to run other, multiple, operating systems. For example, you might run VMware on Linux and run Linux, Windows and Solaris virtual machines.