Modeling and simulation of storage area networks

Storage area networks (SANs) are an emerging data communications platform which interconnects servers and storage devices (such as disks, disk arrays, and tape drives) to create a pool of storage that users can access directly. This networking approach reports benefits such as computer clustering, topological flexibility, fault tolerance, high availability, and remote management. In order to evaluate the performance of these systems it is necessary to have the adequate tools. Usually, performance evaluation may be based on analytical modeling or simulation. Each of them differs in their scope and applicability. However the simulation modeling technique offers more freedom, flexibility, and accuracy than the analytical methods. Thus, when evaluating the performance of SANs, simulation modeling should be used. In this paper the issues involved in the modeling and design of a very flexible and easy to use SAN simulator are presented. This tool is able to consider among others, both real-world I/O traces and synthetic I/O traffic, message packetization, faults in links and switches, virtual channels, different routing algorithms, etc. We describe its main internal organization, the basic modeling mechanisms the simulator is based on, the main input parameters and output performance variables. Also, the analysis of preliminary results using I/O traces is presented, showing that the storage network increases self-similarity of the traffic received by servers, latency variations are more important for control messages than for data messages, and links have a low utilization