摘要： 提出了一个在VoD 系统中具有高可用性的动态容错算法。针对分布式应用的特点，能对控制节点实现服务器切换的容错，数据服务节点负载均衡分配和故障节点提供服务的恢复。同时按照文章一致性保证机制可以实现媒体服务故障恢复对客户端的透明。通过对系统可用性分析和仿真试验表明，该算法可以有效地提高系统的可用性。

关键词: 容错；负载均衡；服务器切换

Abstract: In this paper, a dynamic fault tolerant algorithm is presented for highly available distributed video on demand (VoD) systems.According to the performance requirements of the distributed applications, the load balancing is introduced into fault tolerance. Different server switching methods in different ways according to their functions are presented, which preserve reliability and real-time of the system. System consistency is guaranteed after server switching, which makes the clients unaware of change. The switching between the faulty server and the new server is smooth and it is transparent to the client. Feasibility of this algorithm is analyzed. Experiments indicate that the algorithm effectively improves the reliability of the VoD systems.

Key words: Fault tolerant; SLB; Server switching