Redundant arrays of inexpensive disks (RAID) are a high performance, high reliability and low cost secondary storage subsystems. The purpose of this thesis is to study the factors that can affect one of the main features of RAID systems: performance. For this, I present an analytical model for the response time or RAID levels 0, 1, 01 and 5 based on queuing theory. The results of the model are validated via simulation. From the results of the model and the simulation, the impact of different factors is studied, specially the ones related to the RAID system configuration and the system workload.