From owner-freebsd-performance@FreeBSD.ORG Sat Aug 21 08:46:19 2004 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3E8B716A4CE; Sat, 21 Aug 2004 08:46:19 +0000 (GMT) Received: from ozlabs.org (ozlabs.org [203.10.76.45]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9726343D49; Sat, 21 Aug 2004 08:46:16 +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 821A42BD68; Sat, 21 Aug 2004 18:46:14 +1000 (EST) Received: by blackwater.lemis.com (Postfix, from userid 1004) id D954C51201; Sat, 21 Aug 2004 18:16:12 +0930 (CST) Date: Sat, 21 Aug 2004 18:16:12 +0930 From: Greg 'groggy' Lehey To: Pawel Jakub Dawidek Message-ID: <20040821084612.GH92256@wantadilla.lemis.com> References: <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> <20040820223446.GA18838@panzer.kdm.org> <20040821080614.GC30151@darkness.comp.waw.pl> <20040821083207.GG92256@wantadilla.lemis.com> <20040821083757.GE30151@darkness.comp.waw.pl> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="7cm2iqirTL37Ot+N" Content-Disposition: inline In-Reply-To: <20040821083757.GE30151@darkness.comp.waw.pl> 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: Wilko Bulte cc: Poul-Henning Kamp cc: "Kenneth D. Merry" cc: freebsd-performance@FreeBSD.org Subject: Re: RAID-3? (was: cvs commit: src MAINTAINERS) X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 21 Aug 2004 08:46:19 -0000 --7cm2iqirTL37Ot+N Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Saturday, 21 August 2004 at 10:37:57 +0200, Pawel Jakub Dawidek wrote: > On Sat, Aug 21, 2004 at 06:02:07PM +0930, Greg 'groggy' Lehey wrote: > +> On Saturday, 21 August 2004 at 10:06:14 +0200, Pawel Jakub Dawidek wrote: > +> > So as you can see there are no difference in reading (actually > +> > reading in degraded mode is even a bit faster, hard to say why). > +> > +> I would have half expected this. If you're reading parity as well, > +> then without spindle sync it will take longer for three I/Os to > +> complete than 2. > > I'm not sure if I understand you well... I think you understood what I said, but it looks like it was based on a misassumption. > In RAID3, when array is complete you don't use parity component for > reading at all. So in complete mode, as well as in degraded mode > RAID3 is using only two components for reading. OK, that seems reasonable. phk suggested that you would check parity on reads. Yes, in that case you'd expect things to be identical. Greg -- Note: I discard all HTML mail unseen. Finger grog@FreeBSD.org for PGP public key. See complete headers for address and phone numbers. --7cm2iqirTL37Ot+N Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (FreeBSD) iD8DBQFBJwvUIubykFB6QiMRAg8xAKCKid9G6RFJEPAYsu10eU6W9PfciQCgopuP Qvwfa0eo4N+QOd6XItfv7JU= =dCEj -----END PGP SIGNATURE----- --7cm2iqirTL37Ot+N--