Automated QoS Support for Multimedia Disk Access

This paper describes the AutoQoS mechanism, which improves the timeliness of disk accesses for multimedia applications without requiring any explicit information about their constraints. Multimedia applications typically have periodic time constraints, meaning that they must complete data processing at periodic intervals in order to function correctly. This requirement extends to the disk system, because the application must access data on time in order to meet deadlines. By using Quality of Service algorithms for disk services, an application may receive enough bandwidth and isolation from other disk accesses to read data on time. Nevertheless, past approaches are restrictive because they require that disk bandwidth or deadlines be known and specified in advance. Our system infers from I/O behavior the bandwidth requirement of multimedia streams, and automatically adjusts allocations in order to provide Quality of Service without knowing the constraints or requiring intervention from the application.