Considering common mode failure (CMF) in the rendering cluster systems, the availability of rendering cluster systems with the increase of cluster’s number was studied. Firstly, based on availability of system with one cluster node, system with two cluster nodes was modeled with continuous time markov chain (CTMC) model. Then, the CTMC model was extended to the case of system with three cluster nodes. Furthermore, by solving these three CTMC models, availability for different cases were numerically deduced. Additionally, during one year the unavailable time for different cases was calculated and analysis by comparison was conducted. Finally, conclusions on different cases’ advantages and disadvantages are derived thereby, which offers theoretical foundations for establishing rendering cluster systems.