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Integrated Parellel Prefetching and Caching

Report ID:
November 1995
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Recently there have been a lot of interests in prefetching on
parallel disks. Prefetching is
considered an important technique to exploit
the parallelism on multiple disks for serial applications.
Studies have also shown that for optimal performance,
it is important
to integrate prefetching and caching.
In this paper, we study integrated parallel prefetching
and caching strategies for multiple disks.
We present two algorithms, {em regular aggressive} and
{em reverse aggressive}, and give evidence that
{em reverse aggressive} is close to optimal.
Using trace-driven simulation with a collection of
file access traces, we evaluated these algorithms under a
variety of data placement policies including striping and
Our results show that both algorithms can achieve near
linear speedup when the load is distributed evenly on disks,
and {em reverse aggressive} performs well even when the data
placement policy distributes the load unevenly
[introduce load unbalance?].
In particular, the results show that when prefetching is
done well, the striping data placement strategy perform
close to replicating data across all of the disks.
We also evaluate four online variations of the algorithms
and show that the online algorithms perform well even
with moderate advance knowledge of future file accesses.

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