Reliability modeling of SCI ring-based topologies

Reliability prediction is an important factor in the study of multiprocessor and cluster interconnects. One such interconnect is the scalable coherent interface (SCI), a point-to-point, ring-based interconnect that can be connected into switched ring topologies. However, the reliability of SCI-based topologies cannot be deduced from earlier network reliability work as link failures within an SCI-based interconnect are not independent of one another. This paper presents the results of a reliability study on 1D and 2D k-ary n-cube switching fabrics for SCI based on the elimination of rings rather than of links. The reliability models were created in UltraSAN and verified using analytical modeling. The results show that the reliability of a single-ring system can be greatly enhanced by the addition of a redundant ring yet the reliability of a torus does not increase significantly with additional redundant rings. Hence, the benefit of adding redundant rings is dependent both upon the topology and the degree of reliability sought.