If we are asked to sum up cloud computing in four key words we might arguably choose ‘web’, ‘elasticity’, ‘utility’ and ‘scalability’. In this chapter, we are going to look at the technology underlying the cloud. Cloud applications are accessed via the web, and web technology is integral to the cloud, so we will begin with a brief review of the current state of web technology. We will then move on to virtualisation, a key cloud technology which has many benefits including improved use of resources. Virtualisation can be used to provide the elasticity required to offer cloud computing as a utility. We then turn our attention to the MapReduce programming model, originally developed by the founders of Google and now used to provide scalability to many of the distributed applications which are typical of the cloud and simply too big to be handled in a user-friendly time frame by traditional systems.
KeywordsVirtual Machine Cloud System Physical Machine Java Virtual Machine Cloud Application
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