| For recent years, to satisfy the increasing access loading requirements of Internet video services, VOD system is likely to face a number of challenges at both the network and server side. With the network bandwidth increasing much faster than the server capacity, more and more bottlenecks will be observed on the server side. Cluster becomes a comparative ideal method for enhancing the performance of video server because of its load balancing, high-availability and scalability. This paper made a systematic research of the VOD video server cluster system design and implementation, and tried to use a distributed architecture to make common PCs a video server with load balancing, high-availability, scalability and high-performance for the purpose of building a large-scale video server system.After analyzing the basic structure of VOD system and cluster technology, we proposed a VOD video server cluster model which is consisting of Wide Area Network (WAN) framework and Local Area Network (LAN) framework. The distributed VOD system under WAN framework includes a center and several sub-centers, and every sub-center works in a LAN which has a video server cluster system in it. A video server cluster also includes two parts: a cluster management node and several video service nodesFirstly, the design for load balancing, high-availability and scalability of LAN video sever cluster system is described. Load balancing is implemented by the load balancing scheduling component, which is on the cluster management node of video sever cluster system, by using certain load balancing algorithm. The paper presents a load balancing algorithm in applying to VOD server based on a study of common load balancing algorithms while considering the characteristics of video files, like storage, playing mode and stream rate. High-availability scheme of cluster management node and video service node are discussed. To avoid single point of failure, cluster management node uses a backup. And video service node uses heartbeat message to connect with cluster management node which can detect and take over its failure. Dynamic extension can add video service nodes without changing the current running status. In addition, schemes for load balancing and scalability of a video server applied to WAN are discussed.The operating system of VOD server is Linux, so Linux virtual server (LVS) is used for building the video server cluster. The approach of implementing a LVS video server cluster is described detailedly. It also gave a full implementation of interactive functions for cluster management node, video service node and client side. Through testing, it shows the load balancing, high-availability and scalability of this video server, and proves that using the cluster scheme can achieve the requirement for improving performance. |
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