\begin{abstract}
The motivation for the research presented here is to
develop algorithms for scheduling I/O operations in
parallel computer systems. In order to identify existing
applicable algorithms, a general model for specifying
scheduling problems is first developed. The model is of
interest in its own right; for instance, we have demonstrated its
coverage of algorithms for scheduling parallel tasks with
precedence constraints on multiprocessors.
The model is used to establish an algorithm for scheduling
of I/O operations across a multiple bus I/O architecture
for a multiprocessor system such as the IBM RP3, by
adapting an algorithm used for scheduling of
satellite-switched time-division multiplexed communication
systems with tree structured architectures. The model then
helps recognize that this problem is equivalent to
a more general and previously unstudied problem, namely
scheduling parallel I/O operations in the presence of a
limited class of mutual exclusion constraints, thus
providing an optimal algorithm for the latter problem.
%{\bf Keywords:} Parallel I/O, scheduling, scheduling
%models, data transfer, parallel processing.
\end{abstract}