From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Small Subject: Western Digital Velociraptor WD740ADFD-00NLR5 - NCQ performance falls off a cliff wi queue depth greater than two Date: Mon, 12 Oct 2009 15:18:48 +0100 Message-ID: <4AD33AC8.6000505@seoss.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from relay1.allsecurenet.com ([63.246.152.102]:46439 "EHLO relay1.allsecurenet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756682AbZJLPAV (ORCPT ); Mon, 12 Oct 2009 11:00:21 -0400 Received: from [78.105.152.189] (helo=zebedee.buttersideup.com) by relay1.allsecurenet.com with esmtpsa (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.63) (envelope-from ) id 1MxLjc-0000kX-FT for linux-ide@vger.kernel.org; Mon, 12 Oct 2009 14:18:48 +0000 Received: from [91.208.163.30] (ermintrude [91.208.163.30]) by zebedee.buttersideup.com (Postfix) with ESMTP id 901359B8F5 for ; Mon, 12 Oct 2009 15:18:46 +0100 (BST) Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: linux-ide@vger.kernel.org Hello, I have what looks like a firmware or design performance bug with some 74G WD Velociraptors WD740ADFD-00NLR5 (firmware 21.07QR5). Sequential read speed (as measured with 'hdparm -t') drops-off with NCQ depths greater than 2. Queue-depth(cmds) Speed(MB/s) 1 84 2 84 3 46 5 39 10 39 20 44 31 36 The speed given is the best of 10 - the system was under light load (I couldn't completely unload it, unfortunately). Western Digital helpfully suggested that I contact my Linux vendor... The system is a Tyan server with a Core2Quad Q6600 @ 2.40GHz, and an ICH9 running Debian 5.0 - kernel 2.6.26-2-openvz-amd64, SATA ports in non-RAID/AHCI/native mode. I measured the speed like this: for i in {1..31} ; do echo $i > /sys/block/sda/device/queue_depth ; echo -n "$( cat /sys/block/sda/device/queue_depth | head -c -1 )," ; for j in {1..10} ; do (hdparm -t /dev/sda | egrep -o '[[:digit:]]+\.[[:digit:]]+[[:space:]]+MB/sec' | head -c -1 ) ; done ; echo ; done | sed 's/ MB\/sec/,/g' ... and created a chart and max speed data in openoffice: http://buttersideup.com/files/wd-raptor-NCQ-bug-1.pdf with a second run here: http://buttersideup.com/files/wd-raptor-NCQ-bug-2.pdf Any comments or suggestions welcome - I'd be happy to repeat the test using a different benchmark if anyone can suggest a command-line they'd like run? Cheers, Tim. -- South East Open Source Solutions Limited Registered in England and Wales with company number 06134732. Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ VAT number: 900 6633 53 http://seoss.co.uk/ +44-(0)1273-808309