(S)ATA performance in FBSD 6.2/7.0

R. B. Riddick arne_woerner at yahoo.com
Fri Mar 2 11:02:38 UTC 2007

--- "O. Hartmann" <ohartman at zedat.fu-berlin.de> wrote:
> Before digging into this problem deeper with benchmarks, could anyone 
> explain why FreeBSD reaches this 33 MB/s limit (sounds like UDMA 33 
> defaults, but on both boxes nForce4 and ICH5 controller are recognized 
> and show up with SATA300 or SATA150 capabilities, respective)? May I 
> have some knobs I'm not aware of to tune disk performance?
I think, this 33MB/sec limit comes like this:
The regular copy process (I think u used "cp") reads with speed S from disk A
and writes with speed S to disk B. But: While it reads, it doesnt write AND
while it writes, it doesnt read.

So you might want to try this:
dd if=/diskA/fileA bs=128k | dd of=/diskB/fileB bs=128k

You could also try just to read or to write. Or to read&write with
_independent_ processes.


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