From owner-cvs-all@FreeBSD.ORG Thu Aug 19 06:28:51 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 A9C3216A4CE for ; Thu, 19 Aug 2004 06:28:51 +0000 (GMT) Received: from mail2.speakeasy.net (mail2.speakeasy.net [216.254.0.202]) by mx1.FreeBSD.org (Postfix) with ESMTP id 41E9543D7B for ; Thu, 19 Aug 2004 06:28:51 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: (qmail 27714 invoked from network); 19 Aug 2004 06:28:51 -0000 Received: from gate.funkthat.com (HELO hydrogen.funkthat.com) ([69.17.45.168]) (envelope-sender ) by mail2.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 19 Aug 2004 06:28:50 -0000 Received: from hydrogen.funkthat.com (bqjylq@localhost.funkthat.com [127.0.0.1])i7J6SnuU064578; Wed, 18 Aug 2004 23:28:50 -0700 (PDT) (envelope-from jmg@hydrogen.funkthat.com) Received: (from jmg@localhost) by hydrogen.funkthat.com (8.12.10/8.12.10/Submit) id i7J6Smcu064577; Wed, 18 Aug 2004 23:28:48 -0700 (PDT) Date: Wed, 18 Aug 2004 23:28:48 -0700 From: John-Mark Gurney To: "Greg 'groggy' Lehey" Message-ID: <20040819062848.GM99980@funkthat.com> References: <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> <41244217.6010102@samsco.org> <20040819062228.GO85432@wantadilla.lemis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040819062228.GO85432@wantadilla.lemis.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: Scott Long cc: src-committers@FreeBSD.org cc: Pawel Jakub Dawidek cc: cvs-src@FreeBSD.org cc: cvs-all@FreeBSD.org cc: Poul-Henning Kamp cc: Wilko Bulte Subject: Re: RAID-3? X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: John-Mark Gurney List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Aug 2004 06:28:51 -0000 Greg 'groggy' Lehey wrote this message on Thu, Aug 19, 2004 at 15:52 +0930: > > Your quoted text also seems a bit subjective as there are very valid > > reasons for RAID-3, especially if one is looking for consistent > > low-latency transactions like in video recorders and servers. > > Well, I did use *exactly* this example. I also pointed out that the > relative performance of modern disk subsystems is adequate for a > single streaming video channel. > > Low latency depends on the number of concurrent accesses. RAID-3 > handles concurrent access poorly, exactly because it accesses all > disks for each transfer. One thing that RAID-3 has is that you never have to do a READ/MODIFY cycle when you do writes. Until we implement a write-through cache geom module, raid-5 will continue to substandard performance. -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."