Inconsistent IO performance

[Kevin Oberman]

> From: Ivan Voras <ivoras at freebsd.org>
> Date: Mon, 16 Aug 2010 15:03:23 +0200
> Sender: owner-freebsd-stable at freebsd.org
> 
> On 13.8.2010 18:01, Kevin Oberman wrote:
> > For some time I have seen very odd issues with IO performance on
> > 8-Stable. Going back to November of last year when 8.0 was released, I
> > see variations of up to 22% in identical operations. This is not a
> > degradation as the performance moves up and down.
> 
> In 8.0-8.1 span of time there was some work on the ata driver to make it
> use MAXPHYS (128 KiB) transfer sizes instead of 64 KiB. Modifying this
> will involve changing and recompiling the kernel but if you want to try
> something and the hardware is SATA you might try the new AHCI driver
> ("ada").
> 
> http://ivoras.net/blog/tree/2009-11-17.trying-ahci-in-8.0.html

Thanks. I appreciate the suggestion.  I am running a 8-Stable kernel
from August 9, so I think I should be OK on this. IS there a requirement
to set some parameter in the kernel config to take advantage of this?

While the ThinkPad has a SATA ICH6-M chip-set, it does not provide or any
SATA connections. Both SATA ports a run to a SATA/PATA converter chip
and the only 2 physical connections available are PATA. I am assuming
that this is because 2.5 in. SATA drives were pretty much unavailable
when this system was shipped. This was the last of the T43 series and
was dropped from the product line by Lenovo about a month after I got
it, to be replaced by T60 systems running Core2 chips and using SATA
drives.

Just lousy timing almost 4 years ago.

Thanks again!
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
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