The Cdn Streaming Media Server Io Mechanism Of Realization

The subject of this paper is one of sub-subjects of"Development of supporting system of IPV6 Stream distribution application system", supported by"research of the IPV6 based next generation internet key technology and industrialization promotion"of Beijing Municipal Science and Technology Commission. Along with the rapid evolution of the internet, streaming media service such as VOD and IPTV becomes more and more popular, so we need a high performance and flexible Content Distribution Network to support these services. The performance of Storage server,especially I/O part is the most import in the whole system. This paper first introduces the background, evolution and present of CDN, P2P technology, then gives the overview of PPCDN's architecture, based on this, make an analysis and compare from aspects of I/O model, server architecture, event-inform mechanism, file system, Raid, then chooses the suitable ones for PPCDN system.The storage server is developed under Linux using modularization idea. All modules are running on an asynchronous event driven service runtime framework. Based on some common network service framework, our framework is optimized for the high network IO and high disk IO, using the newest feature Epoll from Linux 2.6 kernel. It provides a uniform interface for registering event and handling the asynchronous event callback. Design and implement a high performance asynchronous Disk IO module. Special mapping function is also used to map meta-data to the file in disk, aiming at decreasing directory depth and offering balance distribution. To speed up meta-data query, the file meta-data in memory is managed via hash table. Storage server implements the BT protocol resolution. Design and implement the function of file distribution using BT technology. At last, this paper introduces the deployment of PPCDN system in Hangzhou, by analyzing the network data and end-users'experience before and after deployment in Huangzhou, we can see that PPCDN system greatly reduces network pressure and improves end-users'experience.