CS631 Paper Response Form
Paper Title: Disk scheduling in a multimedia I/O system
Author(s): A.L.N. Reddy and J. Wyllie
Main Point(s):
The authors propose a new scheduling algorith (SCAN-EDF) that combines
the advantages of seek-time optimizing schedules like SCAN with optimal
real-time schedules like EDF. To meet the real-time requirements, SCAN-EDF
executes the tasks in order of their deadlines. Tasks with the same deadline,
however, are executed in SCAN-order, i.e. ordered by track number. The resulting
schedule strikes a good balance by providing excellent response time for aperiodic
requests while supporting more streams than EDF. The latter is more pronounced
if the deadlines are extended to muliples of the request period and bigger buffers are
used. It is also shown that extending deadlines yields a better tradeoff than
transfering larger chunks of data and that the proposed schedule works good with
RAIDs and multiple data rates.
Possible Use(s):
One of the main problems of multimedia is still how to process the huge amount of
data fast, and optimizing disk access is absolutely critical for that unless
multimedia data is really going to be stored in RAMs or EPROMs.
Extensions:
I don't know what network people are working on, but it seems to me that the same
set of problems and solutions also applies to networking: grouping video requests to
TimeWarner in request periods and ordering them so as to optimize data retrieval time,
trading off response time versus number of clients that can be served simultaneously
versus data chunk size/buffer size. So, it should be possible to perform similar
experiments and data analyses for that problem, although it may be harder to model.
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