From owner-freebsd-current@FreeBSD.ORG Sat Nov 6 23:30:36 2004 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 7AF9B16A4DE for ; Sat, 6 Nov 2004 23:30:36 +0000 (GMT) Received: from blackwater.lemis.com (wantadilla.lemis.com [192.109.197.135]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4282643D31 for ; Sat, 6 Nov 2004 23:30:35 +0000 (GMT) (envelope-from grog@lemis.com) Received: by blackwater.lemis.com (Postfix, from userid 1004) id 3CF5685650; Sun, 7 Nov 2004 10:00:33 +1030 (CST) Date: Sun, 7 Nov 2004 10:00:33 +1030 From: Greg 'groggy' Lehey To: Julian Elischer Message-ID: <20041106233033.GL24507@wantadilla.lemis.com> References: <002401c4bf9c$c4fee8e0$0201000a@riker> <1099286568.4185c82881654@picard.newmillennium.net.au> <4186EDD1.8090805@elischer.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kaF1vgn83Aa7CiXN" Content-Disposition: inline In-Reply-To: <4186EDD1.8090805@elischer.org> User-Agent: Mutt/1.4.2.1i 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: Alastair D'Silva cc: current@freebsd.org Subject: Re: Gvinum RAID5 performance X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 06 Nov 2004 23:30:36 -0000 --kaF1vgn83Aa7CiXN Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable [Format recovered--see http://www.lemis.com/email/email-format.html] Long/short syndrome On Monday, 1 November 2004 at 18:15:45 -0800, Julian Elischer wrote: > Brad Knowles wrote: > >> At 4:22 PM +1100 2004-11-01, Alastair D'Silva wrote: >> >>> The offshoot of this is that to ensure data integrity, a >>> background process is run periodically to verify the parity. >> >> That's not the way that RAID-5 is supposed to work, at least not >> the way I understand it. I would be very unhappy if I was using a >> disk storage subsystem that was configured for RAID-5 and then >> found out it was working in this manner. At the very least, I don't >> believe that we could/should do this by default, and adding code to >> perform in this manner seems to me to be unnecessary complexity. > > You need the background task to read the blocks on the parity stripe > because if you only ever get good reads from teh data stripes and > never read the parity stripe you may grow bad sectors there which > you will not detect until you need then and by then its too late. It > need sto be run at a very low priority however so as to not > interfere with production. That's a possibility, but it's not implemented in old Vinum, and I think Lukas has other issues to address right now. Greg -- When replying to this message, please take care not to mutilate the original text. =20 For more information, see http://www.lemis.com/email.html See complete headers for address and phone numbers. --kaF1vgn83Aa7CiXN Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (FreeBSD) iD8DBQFBjV6ZIubykFB6QiMRAq6aAJ9WYjHw2mrgoLduyGIlBsVMT5EdKACeLvOR 8W2gnMsZHwz/8roXvZBReO8= =cBxC -----END PGP SIGNATURE----- --kaF1vgn83Aa7CiXN--