Two emerging serial storage interfaces for supporting digital libraries: serial storage architecture (SSA) and fiber channel-arbitrated loop (FC-AL)

Digital libraries require not only high storage space capacity but also high performance storage systems which provide the fast accesses to the data. These requirements can not be efficiently supported with the traditional SCSI interfaces. Several serial storage interfaces have been proposed for constructing storage systems with high transfer bandwidth, large storage capacity, and fault tolerance feature. Among them, Serial Storage Architecture (SSA) and Fibre Channel-Arbitrated Loop (FC-AL) are considered as the next generation storage interfaces with broad industry support. Both technologies support simple cabling, long transmission distance, high data bandwidth, large capacity, fault tolerance, and fair sharing of link bandwidth. In this paper, a tutorial and a comparison of these two technologies are presented. The tutorial examines their interface specifications, transport protocols, fairness algorithms, and capabilities of fault tolerance. The comparison focuses on their protocol overhead, flow control, fairness algorithms, and fault tolerance. The paper also summarizes the recently proposed Aaron Proposal which incorporates features from both SSA and FC-AL and targets at merging these two technologies.