From owner-freebsd-current@FreeBSD.ORG Wed Mar 30 22:02:26 2005 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0ACA116A4CE for ; Wed, 30 Mar 2005 22:02:26 +0000 (GMT) Received: from mail22.sea5.speakeasy.net (mail22.sea5.speakeasy.net [69.17.117.24]) by mx1.FreeBSD.org (Postfix) with ESMTP id B837F43D46 for ; Wed, 30 Mar 2005 22:02:25 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: (qmail 17009 invoked from network); 30 Mar 2005 22:02:25 -0000 Received: from gate.funkthat.com (HELO hydrogen.funkthat.com) ([69.17.45.168]) (envelope-sender ) by mail22.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 30 Mar 2005 22:02:23 -0000 Received: from hydrogen.funkthat.com (yjsbap@localhost.funkthat.com [127.0.0.1])j2UM2MGH086942; Wed, 30 Mar 2005 14:02:22 -0800 (PST) (envelope-from jmg@hydrogen.funkthat.com) Received: (from jmg@localhost) by hydrogen.funkthat.com (8.12.10/8.12.10/Submit) id j2UM2Md2086941; Wed, 30 Mar 2005 14:02:22 -0800 (PST) Date: Wed, 30 Mar 2005 14:02:22 -0800 From: John-Mark Gurney To: Martin Nilsson Message-ID: <20050330220221.GH37984@funkthat.com> Mail-Followup-To: Martin Nilsson , freebsd-current@FreeBSD.org References: <20050330191824.4c08acc6.aka@veco.ru> <20050330090813.B64732@carver.gumbysoft.com> <424B0614.5000902@gneto.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <424B0614.5000902@gneto.com> User-Agent: Mutt/1.4.1i X-Operating-System: FreeBSD 4.2-RELEASE i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html cc: freebsd-current@FreeBSD.org Subject: Re: ciss(4): speed degradation for Compaq Smart Array [edited] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: John-Mark Gurney List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Mar 2005 22:02:26 -0000 Martin Nilsson wrote this message on Wed, Mar 30, 2005 at 22:03 +0200: > Doug White wrote / skrev: > > > >I'd also suggest using a tool like iozone to run your tests instead of dd. > >Unless your workload consists of entirely sequential writes this perf test > >is worthless. > > What is wrong with using dd to measure max read/write bandwith of the > controller-disk system? It's not just measuring the bandwidth of the disk system, since it also must read from somewhere first.. So all of your numbers read x bytes from /dev/zero (or else where) and writes x bytes to disk, or read x bytes from disk and writes x bytes to /dev/zero... It is much more optimial to skip the read/write to /dev/zero, and programs like bonnie do this... (Though the cost of modern read/write from/to /dev/zero, it is still measurable.) -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."