Abstract
Virtualization has become a popular way to make more efficient use of server resources within both private data centers and public cloud platforms. Hypervisors are widely used in cloud environments and their impact on application performance has been a topic of significant research and practical interest. While recent advances in CPU architectures and new virtualization techniques have reduced the performance cost of using virtualization, overheads still exist, particularly when multiple virtual machines are competing for resources. The paper will cover the comparisons of some hypervisors based on their performace. The hypervisors which are to be compared are XEN, VMware, KVM, Hyper-V. Thus, the paper gives a brief idea about each hypervisors and theirs performances at different levels