A Real-Time Fault-Tolerant Scheduling Algorithm for Distributed Systems Based on Deferred Active Backup-Copy

The primary/backup copy scheme plays a vital role in the context of real-time fault-tolerant scheduling based on distributed systems. However, traditional active backup copies are required to be completely executed on the backup processors even in fault-free scenario, thereby increasing unnecessary redundancies. In this paper, a novel deferred active backup-copy technique is proposed which is integrated with the fixed-priority scheduling algorithm to exploit redundancies of active backup copies. The proposed technique exploits the processor redundancies through scheduling active backup copies as late as possible and terminating the execution of backup copies when corresponding primary copies are successfully completed. Moreover, based on the aforementioned technique, a “best-fit” heuristic algorithm is designed with the aim of achieving minimal number of processors. Therefore, compared with similar algorithms, this algorithm can further reduce processors needed while guaranteeing real-time and fault-tolerant properties of distributed systems. Finally, simulation experiments are carried out to prove the feasibility and effectiveness of the algorithm.