This book gives an overview of Cloud Computing and Virtualization. It discusses the issues in Computational Resource Allocation and does an extensive experiments to evaluate the performance of web servers hosted on virtual operating systems. As multiple operating systems run on a single physical server, and multiple servers are running in the data center all connected via high speed network links, at some point of time, one of the servers may be overloaded, while others may remain underutilized. This poses challenges related to distributing the load and to carry out the work perfectly by using load balancing algorithm over the virtual machines. This book tries to find out the insights to balance the load based on computational time parameter of the virtual machines. We have also tried to evaluate and compare the performance of the web servers on different virtualization softwares including Xen, OpenVZ and Linux Operating Systems. It also discusses few algorithms related to resource allocation using control theory concepts and distributed computing algorithms.