A video-on-demand (VOD) server needs to store hundreds of movie titles and to support thousands of concurrent accesses. We define the 'access profile' as the number of concurrent accesses to each movie title that should be supported by a VOD server. A current high-end magnetic disk array can only support tens of MPEG-2 concurrent accesses, and it is necessary to replicate and/or stripe the hot movie files over multiple disk arrays. How to replicate, stripe and place the movie files over a minimum number of magnetic disk arrays such that a given access profile can be supported is an important problem. In this paper, we formulate and solve this problem. The result of this study can be applied to the design of the storage subsystem of a VOD server to economically minimize the cost or to maximize the utilization of disk arrays.
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