Inconsistent IO performance

[Roland Smith]

On Sun, Aug 15, 2010 at 12:37:03PM -0700, Kevin Oberman wrote:
> OK. It's pretty clear that disk IO is terrible on this system. I suspect
> it's the SATA/PATA converter that is the throttle. In any case,
<snip>
> I still have no explanation for the variation. It's not vibration. Some
> of my best times were while the system was sitting in my trunk while
> commuting from my home to work. So have some of the worst.

If the performance is craptastic due to the SATA/PATA convertor, could that
also not be a good explanation for the variation? With the different speeds on
the two busses, there might well be variation between the time it takes for
commands to get through (altough one would expect that to even out over time).

Of course to test that you'd have to hook up a harddisk that doesn't need the
convertor... If that improves the situation, you've found the problem.

> I can only hope that my next laptop, which should have ACHI, will improve
> the situation. I'll probably be getting a new laptop in the spring, so
> it won't be too long. Almost time to start trying to figure out what to
> buy. 

Well, looking at my laptop's figures, it is possible to get good
throughput. If you get a system with ICH9 chipset (so you can use ahci(4)),
and a 7200 RPM harddisk, and you should be able to reproduce my figures, I
think.

Roland
-- 
R.F.Smith                                   http://www.xs4all.nl/~rsmith/
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