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.