Real-time primary-backup (RTPB) replication with temporal consistency guarantees

The paper presents a real-time primary-backup (RTPB) replication scheme for supporting fault-tolerant real-time applications. It formally defines two types of temporal consistency, namely external temporal consistency and inter-object temporal consistency. By introducing a key concept called phase variance, the authors are able to build temporal consistency models and derive necessary and sufficient conditions that can be used as the basis for update and transmission scheduling that achieve temporal consistency guarantees. Furthermore, they prove that the term phase variance used in the models can be bounded under various scheduling algorithms, namely EDF, rate monotonic and distance-constrained scheduling. A RTPB implementation was developed within the x-kernel architecture on the MK 7.2 microkernel and the results of a detailed performance evaluation is also discussed.