Generalized Standby-Sparing techniques for energy-efficient fault tolerance in multiprocessor real-time systems

The Standby-Sparing (SS) technique has been previously explored to improve energy efficiency while providing fault tolerance in dual-processor real-time systems. In this paper, by considering both transient and permanent faults, we develop energy-efficient fault tolerance techniques for real-time systems deploying an arbitrary number of identical processors. First, we study the Paired-SS technique, where processors are organized as groups of two (i.e., pairs) and SS is applied within each pair of processors directly after partitioning tasks to the pairs. Then, we propose a Generalized-SS technique that partitions processors into two groups containing primary and secondary processors, respectively. The main and backup copies of tasks are executed on the primary and secondary processors under the partitioned-EDF and partitioned-EDL scheduling policies, respectively. The objective is to reduce the overlapped executions of the main and backup copies in order to improve energy savings. Our experimental evaluations show that, for a given system with fixed number of processors, typically there exists a configuration of primary and secondary processors under the Generalized-SS technique that can lead to better energy savings when compared to the Paired-SS technique.