From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: Some NCQ numbers... Date: Wed, 04 Jul 2007 00:29:27 +0400 Message-ID: <468AB1A7.9010201@msgid.tls.msk.ru> References: <468392CE.6010206@msgid.tls.msk.ru> <468A06A0.1020802@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hobbit.corpit.ru ([81.13.94.6]:20759 "EHLO hobbit.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757891AbXGCU3d (ORCPT ); Tue, 3 Jul 2007 16:29:33 -0400 In-Reply-To: <468A06A0.1020802@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Kernel Mailing List , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org Tejun Heo wrote: > Michael Tokarev wrote: [] >> A test drive is Seagate Barracuda ST3250620AS "desktop" drive, >> 250Gb, cache size is 16Mb, 7200RPM. [test shows that NCQ makes no difference whatsoever] > And which elevator? Well. It looks like the results does not depend on the elevator. Originally I tried with deadline, and just re-ran the test with noop (hence the long delay with the answer) - changing linux elevator changes almost nothing in the results - modulo some random "fluctuations". In any case, NCQ - at least in this drive - just does not work. Linux with its I/O elevator may help to speed things up a bit, but the disk does nothing in this area. NCQ doesn't slow things down either - it just does not work. The same's for ST3250620NS "enterprise" drives. By the way, Seagate announced Barracuda ES 2 series (in range 500..1200Gb if memory serves) - maybe with those, NCQ will work better? Or maybe it's libata which does not implement NCQ "properly"? (As I shown before, with almost all ol'good SCSI drives TCQ helps alot - up to 2x the difference and more - with multiple I/O threads) /mjt