From owner-cvs-src@FreeBSD.ORG Thu Aug 19 06:38:51 2004 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 1959916A4CF; Thu, 19 Aug 2004 06:38:51 +0000 (GMT) Received: from ozlabs.org (ozlabs.org [203.10.76.45]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7131343D67; Thu, 19 Aug 2004 06:38:50 +0000 (GMT) (envelope-from grog@lemis.com) Received: from blackwater.lemis.com (blackwater.lemis.com [192.109.197.80]) by ozlabs.org (Postfix) with ESMTP id ADDAD2BDA1; Thu, 19 Aug 2004 16:38:45 +1000 (EST) Received: by blackwater.lemis.com (Postfix, from userid 1004) id ADA10511FE; Thu, 19 Aug 2004 16:08:43 +0930 (CST) Date: Thu, 19 Aug 2004 16:08:43 +0930 From: Greg 'groggy' Lehey To: John-Mark Gurney Message-ID: <20040819063843.GP85432@wantadilla.lemis.com> References: <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> <20040819062848.GM99980@funkthat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="XFI+TFG+M3u0jUjZ" Content-Disposition: inline In-Reply-To: <20040819062848.GM99980@funkthat.com> User-Agent: Mutt/1.4.1i Organization: The FreeBSD Project Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.FreeBSD.org/ X-PGP-Fingerprint: 9A1B 8202 BCCE B846 F92F 09AC 22E6 F290 507A 4223 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-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Aug 2004 06:38:51 -0000 --XFI+TFG+M3u0jUjZ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wednesday, 18 August 2004 at 23:28:48 -0700, John-Mark Gurney wrote: > 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. Even then, RAID-5 might have higher bandwidth under some circumstances. My real question about RAID-3 remains: what use is it? This isn't nit-picking, it's certainly not a criticism of pjd. I just don't see any practical use on FreeBSD machines. Greg -- Note: I discard all HTML mail unseen. Finger grog@FreeBSD.org for PGP public key. See complete headers for address and phone numbers. --XFI+TFG+M3u0jUjZ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (FreeBSD) iD8DBQFBJErzIubykFB6QiMRAjElAKCV0zZKDIz+kktS4IN+5ZFplWKvpACeO3ps lDZBSYVE/r5wu7KkEPb2MvE= =/OdA -----END PGP SIGNATURE----- --XFI+TFG+M3u0jUjZ--