The term Grid to denote a distributed computing and storage environment was coined in 1998 by Ian Foster and Carl Kesselman. It refers to the metaphor of the power grid: computing capacity from a wall outlet and no need to install and maintain complex IT infrastructures on every location that needs access to applications. This grand vision of a globally virtualised IT infrastructure has at this time not yet been materialised in the way the early visionaries had in mind but we do see more and more of its features in operation today.
The major driving forces, from a business perspective, behind Grid are without any doubt the simplification and optimisation of IT resources. Simplification results from the fact that Grid users can concentrate on their business applications instead of having to maintain a complete complex IT infrastructure; optimisation is obtained because data centres do not have to be sized on peak load but can cleverly share the burden; the idea of on-demand computing. Additionally, a globally distributed IT infrastructure is natural in many very large organisations such as IBM, Shell, Philips, NASA, where large computation jobs can be submitted anytime, anywhere and freely float over the globe.
What is Grid computing and how does it differ from other forms of distributed computing? At this point in the history of IT, there are many forms of distributed computing with considerable similarities. This illustrates the vitality of the Grid idea and it does of course not really matter what name is eventually given to the "Unified Global Distributed IT Infrastructure". The most important characteristics of the Grid, mentioned e.g. by Ian Foster, is the fact that the nodes that make up the Grid are not controlled centrally but have their own management and ownership. If this is not the case, the term cluster seems more appropriate. Another characteristic is the use of open, non-proprietary, standards for information exchange between nodes. A third characteristic of the Grid is that it allows for the co-ordinated setting of bvarious qualities of service, dependent on the requirements of the applications that make use of the Grid.