Q-L/MRP: A Buffer Management Mechanism for QoS Support in a Multimedia DBMS

Multimedia database systems (MMDBSs) have to be capable to handle efficiently time-dependent and timeindependent data, and to support Quality-of-Service (QoS). To support continuous playout of time-dependent data, reservations of the limited resources disk I/O bandwidth and network bandwidth have to be combined with appropriate buffer management. Based on the special requirements of the DEDICATION pre-study, i.e., building a cheap prototype system for asynchronous distance education, we have designed the buffer management mechanism Q-L/MRP. QL/MRP is a buffer preloading and page replacement mechanism for multimedia applications with heterogeneous QoS requirements. Q-L/MRP extends L/MRP with two features: (1) it supports multiple concurrent users, and (2) it supports QoS with a dynamic prefetching daemon. This dynamic prefetching daemon is able to dynamically adapt to the changes in network and disk I/O load. Furthermore, QoS requirements from the users like frame rate are mapped into the buffer mechanism. Our performance analysis shows that Q-L/MRP is very suitable for the special environment in DEDICATION and outperforms other buffer management mechanisms. Since we have implemented Q-L/MRP in software only, it is also suitable for other multimedia applications on other systems with different hardware configurations and workloads.