An efficient modular spare allocation scheme and its application to fault tolerant binary hypercubes

Consideration is given to fault tolerant systems that are built from modules called fault tolerant basic blocks (FTBBs), where each module contains some primary nodes and some spare nodes. Full spare utilization is achieved when each spare within an FTBB can replace any other primary or spare node in that FTBB. This, however, may be prohibitively expensive for larger FTBBs. Therefore, it is shown that for a given hardware overhead more reliable systems can be designed using bigger FTBBs without full spare utilization than using smaller FTBBs with full spare utilization. Sufficient conditions for maximizing the reliability of a spare allocation strategy in an FTBB for a given hardware overhead are presented. The proposed spare allocation strategy is applied to two fault tolerant reconfiguration schemes for binary hypercubes. One scheme uses hardware switches to replace a faulty node, and the other scheme uses fault tolerant routing to bypass faulty nodes in the system and deliver messages to the destination node