A flexible real-time hierarchical multimedia archive

We present a hierarchical multimedia archive that can serve complex multimedia requests from tertiary storage. Requests can consist of multiple request units of streamed and non-streamed data. The request units can have arbitrary synchronization patterns. Our scheduler Promote-IT promotes data from tertiary to secondary storage with real-time guarantees. Promote-IT uses an on-line heuristic algorithm to compute feasible schedules and a separate ASAP dispatcher to increase the efficiency of the resource usage. The heuristic algorithm runs in polynomial time. Schedules are optimized to give short response times to incoming requests. Three major problems complicate this scheduling problem. First, the fragments of requested real-time data and their synchronization are unpredictable. Second, the medium switching times in tertiary storage are high, and the number of drives and robots is low compared to the number of removable media. Third, the shared resources in the tertiary storage system create resource contention problems.