Periodic retrieval of videos from disk arrays

A growing number of applications need access to video data stored in digital form on secondary storage devices (e.g., video-on-demand, multimedia messaging). As a result, video servers that are responsible for the storage and retrieval, at fixed rates, of hundreds of videos from disks are becoming increasingly important. Since video data tends to be voluminous, several disks are usually used in order to store the videos. A challenge is to devise schemes for the storage and retrieval of videos that distribute the workload evenly across disks, reduce the cost of the server and at the same time, provide good response times to client requests for video data. In this paper we present schemes that retrieve videos periodically from disks in order to provide better response times to client requests. We present two schemes that stripe videos across multiple disks in order to distribute the workload uniformly among them. For the two striping schemes, we show that the problem of retrieving videos periodically is equivalent to that of scheduling periodic tasks on a multiprocessor. For the multiprocessor scheduling problems, we present and compare schemes for computing start times for the tasks, if it is determined that they are schedulable.