In the context of real-time fault-tolerant scheduling in multi- processor systems, Primary-backup scheme plays an important role. A backup copy is always preferred to be executed as passive backup copy whenever possible because it can take the advantages of backup copy de-allocation technique and overloading technique to improve schedula- bility. In this paper, we propose a novel efficient fault-tolerant rate- monotonic best-fit algorithm efficient fault-tolerant rate-monotonic best-fit (ERMBF) based on multiprocessors systems to enhance the schedulability. Unlike existing scheduling algorithms that start schedul- ing tasks with only one processor. ERMBF pre-allocates a certain amount of processors before starting scheduling tasks, which enlarge the searching spaces for tasks. Besides, when a new processor is allocated, we reassign the task copies that have already been assigned to the exist- ing processors in order to find a superior tasks assignment configuration. These two strategies are all aiming at making as many backup copies as possible to be executed as passive status. As a result, ERMBF can use fewer processors to schedule a set of tasks without losing real-time and fault-tolerant capabilities of the system. Simulation results reveal that ERMBF significantly improves the schedulability over existing, compa- rable algorithms in literature.
