From owner-cvs-all@FreeBSD.ORG Fri Aug 20 22:35:12 2004 Return-Path: Delivered-To: cvs-all@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 81FC416A4CE; Fri, 20 Aug 2004 22:35:12 +0000 (GMT) Received: from panzer.kdm.org (panzer.kdm.org [216.160.178.169]) by mx1.FreeBSD.org (Postfix) with ESMTP id F0D4043D39; Fri, 20 Aug 2004 22:35:11 +0000 (GMT) (envelope-from ken@panzer.kdm.org) Received: from panzer.kdm.org (localhost [127.0.0.1]) by panzer.kdm.org (8.12.9/8.12.5) with ESMTP id i7KMYlui019034; Fri, 20 Aug 2004 16:34:47 -0600 (MDT) (envelope-from ken@panzer.kdm.org) Received: (from ken@localhost) by panzer.kdm.org (8.12.9/8.12.5/Submit) id i7KMYlPQ019033; Fri, 20 Aug 2004 16:34:47 -0600 (MDT) (envelope-from ken) Date: Fri, 20 Aug 2004 16:34:47 -0600 From: "Kenneth D. Merry" To: Pawel Jakub Dawidek Message-ID: <20040820223446.GA18838@panzer.kdm.org> References: <20040817132740.GA32139@freebie.xs4all.nl> <41449.1092750244@critter.freebsd.dk> <200408161043.i7GAhfXs079045@repoman.freebsd.org> <20040817004407.GA81257@wantadilla.lemis.com> <20040817074633.GO30151@darkness.comp.waw.pl> <20040817112900.GA31635@freebie.xs4all.nl> <20040817124020.GK88156@wantadilla.lemis.com> <20040817131612.GT30151@darkness.comp.waw.pl> <20040819024359.GA85432@wantadilla.lemis.com> <20040820193547.GZ30151@darkness.comp.waw.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040820193547.GZ30151@darkness.comp.waw.pl> User-Agent: Mutt/1.4.1i cc: src-committers@FreeBSD.org cc: cvs-src@FreeBSD.org cc: cvs-all@FreeBSD.org cc: Poul-Henning Kamp cc: Greg 'groggy' Lehey cc: Wilko Bulte cc: freebsd-performance@FreeBSD.org Subject: Re: RAID-3? (was: cvs commit: src MAINTAINERS) X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 Aug 2004 22:35:12 -0000 On Fri, Aug 20, 2004 at 21:35:47 +0200, Pawel Jakub Dawidek wrote: > As you can see RAID5 is only faster in READ tests for 15 and 100 processes > working in parallel. As I can see, RAID3 is faster in all the rest tests. > > Of course you are welcome to try by yourself. > > Anyway, if I can ask for something. Think twice before calling something > ridiculous without understanding. > > PS. I wonder about read optimization, so parity component can be also > used for reading in round-robin fashion... That likely wouldn't speed things up too much. The hard drives are doing read ahead anyway, so they'll usually have the data ready when you go down to read the next block if you're doing sequential reads. You would also spend more CPU power to reconstruct the piece of data you didn't read from the disk. That'll probably increase your latency somewhat, and you would also be touching all of the data with the CPU. As PHK said, it might be more interesting to do data integrity checking on reads. The problem, of course, is that you wouldn't be able to correct problems, you would only be able to detect them. Ken -- Kenneth Merry ken@kdm.org