Abstract
Cloud computing technology is one of the biggest milestones in leading us to next generation technology and Booming up business and IT field. It helps to overcome the problems of data loss, accessing data whenever needed and data security. Virtualization is the major technology that works with cloud computing. An actual cloud is implemented with the use of Virtualization technology. Virtualization in cloud computing is making a virtual image of the storage devices servers or network resources so that they can be used on multiple machines at the same time. The cloud infrastructure cost goes very high. Therefore, the concept of virtualization needs to be understood and implement in the cloud computing systems, which enables the user as well as the owners for the better and robust management and usage of the cloud. In this paper the virtualization approach in the cloud computing environment are well presented with the concept of the cloud service models and how virtualization helps to improve elasticity of the resources such as network, server, storage, application and client in cloud computing environment. In addition to this, it gives a detailed review on open source virtualization techniques, challenges and future research directions.