Performance analysis of a fault-tolerant distributed-shared memory protocol on the SOME-bus multiprocessor architecture

Interconnection networks allowing multiple simultaneous broadcasts are becoming feasible, mostly due to advances in fiber-optics and VLSI technology. Distributed-shared-memory implementations on such networks promise high performance even for applications with small granularity. This paper summarizes the architecture of one such implementation, the simultaneous optical multiprocessor exchange bus, and examines the performance of an augmented DSM protocol which provides fault tolerance by exploiting the natural DSM replication of data in order to maintain a recovery memory in each processing node. Theoretical and simulation results show that the additional data replication necessary to create fault-tolerant DSM causes no reduction in system performance during normal operation and eliminates most of the overhead at checkpoint creation. Data blocks which are duplicated to maintain the recovery memory may be utilized by the regular DSM protocol, reducing network traffic, and increasing the processor utilization significantly.