From owner-freebsd-hackers@FreeBSD.ORG  Fri Jan 18 05:51:41 2013
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Subject: Re: IBM blade server abysmal disk write performances
From: Adrian Chadd <adrian@freebsd.org>
To: Dieter BSD <dieterbsd@gmail.com>
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Cc: freebsd-hackers@freebsd.org, gibbs@freebsd.org, scottl@freebsd.org,
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When you run gstat, how many ops/sec are you seeing?




Adrian


On 17 January 2013 20:03, Dieter BSD <dieterbsd@gmail.com> wrote:
>> I am thinking that something fancy in that SAS drive is
>> not being handled correctly by the FreeBSD driver.
>
> I think so too, and I think the something fancy is "tagged command queuing".
> The driver prints "da0: Command Queueing enabled" and yet your SAS drive
> is only getting 1 write per rev, and queuing should get you more than that.
> Your SATA drive is getting the expected performance, which means that NCQ
> must be working.
>
>> Please let me know if there is anything you would like me to run on the
>> BSD 9.1 system to help diagnose this issue?
>
> Looking at the mpt driver, a verbose boot may give more info.
> Looks like you can set a "debug" device hint, but I don't
> see any documentation on what to set it to.
>
> I think it is time to ask the driver wizards why TCQ isn't working,
> so I'm cc-ing the authors listed on the mpt man page.
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