Modeling and performance evaluation of iSCSI storage area networks over TCP/IP-based MAN and WAN networks

This paper provides a concise modeling and performance evaluation of the iSCSI storage area network (SAN) architecture and protocol. SANs play a key role in business continuity, enterprise-wide storage consolidation and disaster recovery strategies in which storage resources are most often distributed over many distant data center locations. In the future, SAN traffic will be transported over IP-based networks, e.g., enterprise virtual private networks, to benefit from converged networks and save cost. In these scenarios, the impact of end-to-end delay and QoS of broadband networks on SAN performance is critical and has to be well understood by IT departments when deploying IP-storage solutions and network operators when designing transport network services for SAN applications. In this context, we propose models for iSCSI write requests over TCP/IP networks, e.g., as used in asynchronous mirroring applications. In addition to the analysis for individual requests we present - to the best of our knowledge for the first time - the evaluation of an iSCSI session under a realistic request traffic model with and without interleaving. We analyze the throughput and total request write times for different network dimensions, i.e., round-trip times, and QoS levels, processing delays in the iSCSI layer as well as request characteristics