副本和代理策略是目前在VoD服务中应用最广泛的两种主流技术方案，都是保证终端用户VoD服务实时流畅的有效手段，但以往的研究都局限于研究单一策略对系统性能的提升。本文提出了一种VoD集群文件副本加代理的复合策略，集群中的服务器作为文件副本服务器存在，而同时又具有内容代理服务器的功能，并建立了相应的数学模型。仿真实验表明，相比单一的策略，副本结合代理的复合策略可以减少30％以上的点播延时，满足系统的负载均衡需求，较大程度地减少重定向引起的延时，提高系统的准入概率。

Caching and replication have emerged as two primary techniques for reducing the delay experienced by endusers when demanding the VoD services.Previous research tends to focus on either one of them separately.The hybrid strategy uses a VoD server both as a replicator and as a proxy server.An analysis model is proposed to predict the benefit of the strategy.The simulation results indicate that saving up to 30% latency is observed ,under various system parameters,compared to standalone replication or caching mechanisms.The hybrid scheme can guarantee the load balancing and thus can provide better QoS guarantee.