This paper presents a framework for reasoning about the timing correctness of multimedia data streams supported on a shared, serially-reusable server. A real-time scheduling approach is used to guarantee the timing requirements for multimedia applications such as video-on- demand and multimedia presentations. This framework incorporates the use of scheduling models, which are defined as abstractions that can be used to reason about timing correctness on physical resources. The scheduling models in this paper can be applied to multimedia systems which use periodic tasks to retrieve data from a disk. With their use, the multimedia system designer can reason a priori about the throughput, capacity, and schedulability of a system. The models enable the real-time system architect to quickly explore the system design space, to establish and maintain a firm performance baseline, to optimize system configuration parameters, and to explore the impact of new technologies. As an example of the application of this framework a new disk policy called T-scan is developed here. T-scan is applied to a multimedia task set and the analytical results are presented. Additionally, the performance of various disk policies are compared using the framework.