A Cascading Redundancy Approach for Dependable Real-Time Systems

Abstract

Dependable real-time systems typically consist of tasks of multiple criticality levels and scheduling them in a faulttolerant manner is a challenging problem. Redundancy in the physical and temporal domains for achieving fault tolerance has been often dealt independently based on the types of errors one needs to tolerate. To our knowledge, there had been no work which tries to integrate fault tolerant scheduling and multiple redundancy mechanisms. In this paper we propose a novel cascading redundancy approach within a generic fault tolerant scheduling framework. The proposed approach is capable of tolerating errors with a wider coverage (with respect to error frequency and error types) than time and space redundancy in isolation, allows tasks with mixed criticality levels, is independent of the scheduling technique and, above all, ensures that every critical task instance can be feasibly replicated in both time and space.

An Efficient Fault Recovery Algorithm in Multiprocessor Mixed-Criticality Systems

“…Papers [2,14] present a generic fault tolerant scheduling framework that allows every critical task to be feasibly replicated in both time and space dimensions. The basic idea is to derive feasibility window to reserve necessary slacks for re-execution of critical, highlycritical and ultra-critical task instances while a best-effort service is provided to non-critical task instances.…”

“…Saraswat et al proposed a task migration scheme for handling permanent faults and check-pointing with rollback recovery for transient faults [10,11]. Aysan et al presented a generic fault-tolerant scheduling framework for mixed-criticality systems [2,14]. Four criticality levels, including non-critical, critical, highlycritical and ultra-critical, are considered.…”