Inconsistent IO performance
freebsd at jdc.parodius.com
Mon Aug 16 15:33:19 UTC 2010
On Mon, Aug 16, 2010 at 07:46:38AM -0700, Kevin Oberman wrote:
> > 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
> Just lousy timing almost 4 years ago.
I should expand on what Kevin's stated (I read what was written 3 or 4
times over and it didn't jive; "if there's no physical SATA connections,
why is a SATA/PATA converter in use?").
The T43 is a bizarre beast. The ICH6-M chipset uses SATA, but is
physically wired to a custom PCB/adapter that serves a couple different
- Converts a 2.5" PATA hard disk connector into SATA (meaning, the
laptop actually uses 2.5" PATA hard disks). thinkwiki.org refers to
this as a "SATA-to-PATA bridge" (controller-to-disk), while I tend to
look at it as a PATA-to-SATA bridge (disk-to-controller).
- Integrates a "middle-man" ASIC that supposedly intercepts ATA
commands, in addition to doing some drive model string verification
(requiring folks to purchase IBM-sanctioned drives).
- The system BIOS knows of the PCB/adapter and, somehow, queries it to
verifies its existence. I imagine it sends some vendor-centric ATA
commands which the ASIC intercepts. Supposedly people have tried
removing (desoldering) the adapter in attempt to use standard SATA
disks and destroyed their systems in the process.
As Kevin stated, the ICH6-M doesn't support AHCI, so using ahci.ko isn't
an option in his case.
It's possible that the adapter in question is going/has gone bad, is
doing something awful, or the underlying drive itself has degraded in
some way which SMART doesn't see (ex. on-disk cache going bad; wouldn't
surprise me in this case).
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
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