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From: Peter Schuller <peter.schuller@infidyne.com>
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Date: Sun, 4 Nov 2007 17:41:34 +0100
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Subject: Re: ZFS Hangs
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> Well the readahead "issues" are just the zfs design, AFAIK.  It does
> aggressive prefetching to improve performance on the assumption that you
> are running with a reasonably fast storage system that can keep up.  On
> crappy low end disk hardware (e.g. single ATA disk) this can easily
> saturate the disk.

Well, regardless of the absolute performance you don't want the read-ahead =
to=20
consume to much of the relative bandwidth/seek time available.

Personally I didn't experience any prooven issues with prefetch; I disabled=
 it=20
on general recommendation back in the i386/1gb days and told myself I saw a=
n=20
improvement. I never looked into it carefully, other than that I previously=
=20
had a general feeling that I saw a lot more I/O on the pool than what was=20
read by applications. My memories are vague.

=2D-=20
/ Peter Schuller

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