Fault-tolerant storage subsystems for video-on-demand servers

A large-scale video-on-demand (VOD) system demands storage of hundreds of movies and support of thousands of concurrent accesses. The number of concurrent accesses to each movie may vary, depending on the popularity of each movie. A VOD access profile keeps the information of the movie titles and the number of concurrent accesses to each movie that should be supported. To ensure high reliability in such service, parity blocks and/or redundant copies of these movie files are maintained. File allocation problem is concerned with how to replicate, stripe, and place the movie files over a number of magnetic disk arrays such that a given access profile can be supported at a minimum cost. In this paper, we study different design schemes of storage subsystems for video on demand services. And we present the Shifted Redundancy with Cyclic Permutation storage subsystem proposed by Wang and Du which is one of the best available schemes.