Quasi-static fault-tolerant scheduling schemes for energy-efficient hard real-time systems

► Quasi-static fault-tolerance task scheduling algorithms consisting of offline components and online components are proposed. ► The algorithms are based on a fault model that considers the effect of DVS on transient fault rate. ► The design of offline components enables the online components to save energy using slack due to uncertainties in fault occurrences. ► The algorithms are validated both under simulation environments and on a reallife hard real-time testbed. This paper investigates fault tolerance and dynamic voltage scaling (DVS) in hard real-time systems. The authors present quasi-static task scheduling algorithms that consist of offline components and online components. The offline components are designed the way they enable the online components to achieve energy savings by using the dynamic slack due to variations in task execution times and uncertainties in fault occurrences. The proposed schemes utilize a fault model that considers the effects of voltage scaling on transient fault rate. Simulation results based on real-life task sets and processor data sheets show that the proposed scheduling schemes achieve energy savings of up to 50% over the state-of-art low-energy offline scheduling techniques and incur negligible runtime overheads. A hard real-time real-life test bed has been developed allowing the validation of the proposed algorithms.