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Date: Sun, 28 Sep 2008 16:59:53 +0200 (CEST)
From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To: Danny Do <ai_quoc@hotmail.com>
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Cc: freebsd-questions@freebsd.org
Subject: RE: Hard disk bottle neck.
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> the following code:
>
> patch /usr/src/sys/sys/param.h
>
> #ifndef DFLTPHYS
> #define DFLTPHYS        (1024 * 1024)   /* default max raw I/O transfer size
> */
> #endif
> #ifndef MAXPHYS
> #define MAXPHYS         (1024 * 1024)   /* max raw I/O transfer size */
> #endif
> #ifndef MAXDUMPPGS
>
> I'll update the result. I'll tell you how I go. Maybe sometimes in the next
> fortnight.
>
> Thanks everyone, thanks Wojciech Puchar,

after you recompile the kernel with that patch, check your disk 
performance in some directory consisting of many large files

cd that_dir
for x in *;do (cat $x >/dev/null &);done

while running systat,:vmstat on another console


i've just did this on one of my systems, with ONE 500GB SATA drive and 
with geli encryption.

got 48MB/s and about 50% CPU load with core2 duo.