The computational world is becoming very large and complex. Cloud computing has emerged as a new paradigm of computing and also has gained attention from both academic and business community. Its utility-based usage model allows users to pay per use, similar to other public utility such as electricity, with relatively low investment on the end devices that access the cloud computing resources. Cloud users can request/rent resources as they become necessary, in a much more scalable and elastic way. A provision should be made so that all resources are made available to the users to satisfy their need.