The main contribution of this book is developing performance models for cloud computing centers. We started off with a basic analytical model and then gradually extended the scope of the model in order to capture most important aspects of nowadays cloud centers. The course steps of the performance model development process are as follows: For the first time, we employed M[x]/G/m/m+r queuing system, which is our abstract model, in order to deal with the performance evaluation of a cloud center under batch arrival (super-tasks). We have extended our analytical model for performance evaluation of highly virtualized cloud computing centers. Our experience with previous performance models revealed that a monolithic model may suffer from intractability and poor scalability due to large number of parameters. Finally, We have extended our proposed interacting analytical model to capture important aspects including pool management, power consumption, resource assigning process and virtual machine deployment of nowadays cloud centers.