Date: Thu, 17 Jan 2013 20:03:56 -0800 From: Dieter BSD <dieterbsd@gmail.com> To: freebsd-hackers@freebsd.org Cc: gibbs@FreeBSD.org, scottl@FreeBSD.org, mjacob@FreeBSD.org Subject: Re: IBM blade server abysmal disk write performances Message-ID: <CAA3ZYrCgMmGi3EHKEuXb=qWPjC2zSMYcfgZ6nh-ipqQ7dAeVdA@mail.gmail.com>
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> 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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