Abstract: In the past decade, there has been a paradigm shift from traditional network computing environment to cloud computing. The reason is increase in the size of data to be stored, transferred and processed from several Megabytes to Terabytes, Petabytes and Exabytes. This paper describes the role of virtualization as technique for improving resource utilization and energy efficient computing in conventional client server environment as well as in modern cloud computing environments.

Keywords: Cloud Computing, Virtualization, Virtual Machine, Cloud Operating Systems, Service Oriented Architecture.