From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: ahci problems with sata disk. Date: Tue, 16 Jan 2007 13:32:26 -0500 Message-ID: <45AD1A3A.4000706@rtr.ca> References: <1168785128.7865.13.camel@duo> <45AB45B2.2080602@gmail.com> <1168859112.6980.8.camel@duo> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from rtr.ca ([64.26.128.89]:1489 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750729AbXAPSc3 (ORCPT ); Tue, 16 Jan 2007 13:32:29 -0500 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Andrew Lyon Cc: linux-ide@vger.kernel.org, Alan Cox , Tejun Heo .. >> I though that NCQ was intended to increase performance ?? .. > My Raptor drive WDC WD740ADFD-00 Rev: 20.0 performs worse with NCQ > than with NCQ, Alan Cox has added it to a blacklist but I dont think > that is in the mainline kernel yet. > > Search the list archives for my previous postings about it, including > some hdparm -tT results. > > Andy Raptors have "server style" firmware in them. When NCQ is turned on, they self-optimize for random seeks rather than for sequential read-ahead. My hdparm test is a sequential read-ahead test, so it will naturally perform worse on a Raptor when NCQ is on. That doesn't mean NCQ is bad on all Raptors; it just means it's not good for large sequential reads. Cheers