AN EVENT-BASED MODEL FOR CONTINUOUS MEDIA DATA ON HETEROGENEOUS DISK SERVERS

Over the last few years, there has been intense work on the problem of retrieval of continuous media (CM) data from disk. However, no single unified framework exists within which such retrieval problems can be studied. In this paper, we first propose a formal model for CM data re trieval from heterogeneous disk servers. This model can be used to cha racterize CM data retrieval problems independently of how data is laid out on disk, and what objectives (e.g., minimize client delay, maximi ze buffer utilization, etc.) the system manager is interested in. We t hen show how using this formal model, we can neatly define what it mea ns to optimally handle events that occur in movie-on-demand (MOD) syst ems. Examples of such events include new clients entering the system, old clients leaving the system, continuing clients doing pause, rewind and fast-forward operations. Multiple events may occur simultaneously and we show how such events trigger state transitions in the system. We then develop an algorithm called the QuickSOL algorithm that handle s events occurring in MOD systems. This algorithm works in two phases: in the first phase, it quickly finds a way of handling as many of the events occurring at time t as possible. In the second phase, it optim izes the solution found in the first phase. The advantage is that the algorithm can be interrupted anytime after the first phase is complete d. We report on experiments showing that QuickSOL works well in practi ce.