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From: Ivan Voras <ivoras@freebsd.org>
Date: Wed, 16 Mar 2011 21:48:13 +0100
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Subject: Re: svn commit: r219699 - head/sys/kern
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On 16 March 2011 21:37, Ivan Voras <ivoras@freebsd.org> wrote:

> For now, there's a report (which actually inspired me to retest and
> commit this) from someone who tried this on 2x 15k RPM SAS drives,
> with much better results using read_max=128 (thread "gmirror
> performance" on freebsd-fs@). I estimate that because his drives were
> 15kRPM from the start, the improvement isn't as drastic going from 8
> to 128 as on these SATA drives I tested on (faster seeks). He went
> from ~~ 195 MB/s to ~~ 258 MB/s while I go from ~~ 50 MB/s to ~~ 140
> MB/s.

Btw I also tested that random IO isn't affected by this: it isn't. The
read-ahead heuristics is working.