Research And Implement Of Load Balancing Model Based On Active Replication Fault-Tolerance

With the rapid development of computer network tech and the depreciation of hardware, it has been a trend to distribute complex computing tasks to many physical hosts to improve computing speed and save computing costs. Such a system is called as Distributed Computing System (DCS). Many computers are connected by communication links serving users as a single computer. DCS provides users rich resources. Many topics in DCS are studied widely such as communicate network, distributed operation system, distributed database, parallel program design, fault tolerance and distributed real-time system, etc.There are several reasons to build a distributed application: resource sharing, better performance, reliability, communication, flexibility, etc. The paper focuses on reliability (fault-tolerance) and performance (load-balancing). Active replication can improve system robust and reduce response time while load balancing improves system performance. However it is observed that redundant resources are wasted in a fault tolerant system when it runs smoothly (no fault). What's more, load balancing are vulnerable when a system fault occurs. Active replication fault-tolerance and load balancing can complement each other. Hence the combination of these two technologies improves both robustness and efficiency in distributed systems.The thesis studies on the combination of fault tolerance with active replication and load balancing. It achieves some creative results. Firstly, after analyzing the status quo of active replication fault-tolerance and load balancing technologies, the thesis proposes a load-balancing model based on active replication fault-tolerance, followed by a hierarchical architecture and three available types of task scheduling structure. The model is able to adjust fault tolerant groups and group membership relations dynamically according to system real-time loading in order to satisfy system throughput and reliability requirement. Secondly, based on fault tolerant system with active replication accomplished by SEU, the thesis enhances the system with load balancing supporting central-control task scheduling. Thirdly, the thesis analyzes the effects of group member computing ability, task distributing policy, redundancy of fault group and task arrival frequency on system performance and fairness in-depth.