This document presents a stochastic model utilizing Stochastic Reward Nets (SRNs) for evaluating data center performance and quality of service (QoS) in IaaS cloud computing systems. The model addresses the challenges associated with existing experimental and simulation approaches, allowing for scalable analysis of thousands of cloud resources and flexible integration of various strategies. It emphasizes performance metrics such as utilization, availability, and responsiveness, enabling system managers to optimize data center parameters effectively.