Loading...
Competitive Parallel Disk Prefetching and Buffer Management
Barve, Rakesh Kallahalla, Mahesh Varman, Peter J. Vitter, Jeffrey Scott
Barve, Rakesh
Kallahalla, Mahesh
Varman, Peter J.
Vitter, Jeffrey Scott
Citations
Altmetric:
Abstract
We provide a competitive analysis framework for online prefetching and buffer management
algorithms in parallel I/O systems, using a read-once model of block references. This has
widespread applicability to key I/O-bound applications such as external merging and concurrent
playback of multiple video streams. Two realistic lookahead models, global lookahead and local
lookahead, are defined. Algorithms NOM and GREED based on these two forms of lookahead
are analyzed for shared buffer and distributed buffer configurations, both of which occur frequently
in existing systems. An important aspect of our work is that we show how to implement
both the models of lookahead in practice using the simple techniques of forecasting and flushing.
Given a
-disk parallel I/O system and a globally shared I/O buffer that can hold upto
disk
blocks, we derive a lower bound of
on the competitive ratio of any deterministic online
prefetching algorithm with
lookahead. NOM is shown to match the lower bound using
global
-block lookahead. In contrast, using only local lookahead results in an
competitive
ratio. When the buffer is distributed into
portions of
blocks each, the algorithm
GREED based on local lookahead is shown to be optimal, and NOM is within a constant factor
of optimal. Thus we provide a theoretical basis for the intuition that global lookahead is more
valuable for prefetching in the case of a shared buffer configuration whereas it is enough to provide
local lookahead in case of the distributed configuration. Finally, we analyze the performance
of these algorithms for reference strings generated by a uniformly-random stochastic process and
we show that they achieve the minimal expected number of I/Os. These results also give bounds
on the worst-case expected performance of algorithms which employ randomization in the data
layout.
Description
Date
2000
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Research Projects
Organizational Units
Journal Issue
Keywords
Citation
R. D. Barve, M. Kallahalla, P. Varman, and J. S. Vitter. “Competitive Analysis of Buffer Management Algorithms for Parallel I/O Systems,” Journal of Algorithms, 36(2), August 2000, 152–181. An extended abstract appears in Proceedings of the ACM-IEEE Workshop on I/O in Parallel And Distributed Systems (IOPADS ’97), San Jose, CA, November 1997, 47–56. http://dx.doi.org/10.1006/jagm.2000.1089