From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Some NCQ numbers... Date: Thu, 05 Jul 2007 15:22:29 -0400 Message-ID: <468D44F5.4070906@tmr.com> References: <468392CE.6010206@msgid.tls.msk.ru> <468A06A0.1020802@gmail.com> <468AB1A7.9010201@msgid.tls.msk.ru> <468AF5BB.10005@gmail.com> <468B6BD7.9010108@msgid.tls.msk.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <468B6BD7.9010108@msgid.tls.msk.ru> Sender: linux-scsi-owner@vger.kernel.org To: Michael Tokarev Cc: Tejun Heo , Kernel Mailing List , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org List-Id: linux-ide@vger.kernel.org Michael Tokarev wrote: > Tejun Heo wrote: >> Hello, >> >> Michael Tokarev wrote: >>> 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". >> I see. Thanks for testing. > > Here are actual results - the tests were still running when > I replied yesterday. > > Again, this is Seagate ST3250620AS "desktop" drive, 7200RPM, > 16Mb cache, 250Gb capacity. The tests were performed with > queue depth = 64 (on mptsas), drive write cache is turned > off. > But... with write cache off you don't let the drive do some things which might show a lot of improvement with one scheduler or another. So your data are only part of the story, aren't they? [snip] >>> By the way, Seagate announced Barracuda ES 2 series >>> (in range 500..1200Gb if memory serves) - maybe with >>> those, NCQ will work better? >> No one would know without testing. > > Sure thing. I guess I'll set up a web page with all > the results so far, in a hope someday it will be more > complete (we don't have many different drives to test, > but others do). > > By the way. Both SATA drives we have are single-platter > ones (with 500Gb models they've 2 platters, and 750Gb > ones are with 3 platters), while all SCSI drives I > tested have more than one platters. Maybe this is > yet another reason for NCQ failing. > > And another note. I heard somewhere that Seagate for > one prohibits publishing of tests like this, however > I haven't signed any NDAs and somesuch when purchased > their drives in a nearest computer store... ;) > >>> 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) >> Well, what the driver does is minimal. It just passes through all the >> commands to the harddrive. After all, NCQ/TCQ gives the harddrive more >> responsibility regarding request scheduling. > > Oh well, I see.... :( > -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot