With improvement in technology, there is huge migration of business applications to cloud. Performance evaluation of cloud computing infrastructure is required to predict and quantify the cost-benefit of a strategy portfolio and the corresponding Quality-of-Service (QoS) experienced by users. Such analyses are not feasible by simulation or on-the-field experimentation, due to great numbers of parameters that have to be investigated. Here, the authors present an analytical model that is scalable to model systems composed of thousands of resources. Several performance metrics defined and evaluated to analyze the performance of cloud data center.