From owner-freebsd-current@FreeBSD.ORG Mon Oct 11 15:56:44 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 8179C16A4D1 for ; Mon, 11 Oct 2004 15:56:44 +0000 (GMT) Received: from gromit.dlib.vt.edu (gromit.dlib.vt.edu [128.173.49.29]) by mx1.FreeBSD.org (Postfix) with ESMTP id 185B843D45 for ; Mon, 11 Oct 2004 15:56:44 +0000 (GMT) (envelope-from paul@gromit.dlib.vt.edu) Received: from hawkwind.Chelsea-Ct.Org (pool-151-199-91-61.roa.east.verizon.net [151.199.91.61]) by gromit.dlib.vt.edu (8.13.1/8.13.1) with ESMTP id i9BFuV8i028056 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 11 Oct 2004 11:56:33 -0400 (EDT) (envelope-from paul@gromit.dlib.vt.edu) Received: from [192.168.1.25] (zappa [192.168.1.25])i9BFuNxL000729; Mon, 11 Oct 2004 11:56:25 -0400 (EDT) From: Paul Mather To: freebsd-current@freebsd.org In-Reply-To: <20041011151506.747E516A4CF@hub.freebsd.org> References: <20041011151506.747E516A4CF@hub.freebsd.org> Content-Type: text/plain Message-Id: <1097510181.99562.18.camel@zappa.Chelsea-Ct.Org> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Mon, 11 Oct 2004 11:56:23 -0400 Content-Transfer-Encoding: 7bit cc: Christian Hiris <4711@chello.at> cc: axel.gruner@suedfactoring.de cc: Chris Elsworth Subject: Re: RAID1 with gmirror 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: Mon, 11 Oct 2004 15:56:44 -0000 On Mon, 11 Oct 2004 14:26:06 +0100, Chris Elsworth wrote: > So, I'm left quite unsure whether the warnings are harmless or not. > Pawel, can we just use existing labels on disks and apply a gmirror > over it, or should we be re-labelling inside the mirror device? I believe it is safer to re-bsdlabel the mirror device rather than use an existing disklabel. Remember, the mirror device uses one sector at the end of each provider to store its metadata. So, if you use the existing provider's disklabel, you will at the very least get complaints concerning the label about the "c" partition extending past the end of the device (because the "c" partition will be one sector too long now). Also, if you are unlucky, the mirror metadata might overwrite (and render inaccessible) a sector's worth of actual filesystem data in the last sector from the original provider when you create the mirror. That could cause problems. Labelling the mirror device ensures that filesystem data is not on any inaccessible sectors (assuming you don't deliberately create an invalid label on the new mirror device:). FWIW, I outline in a posting to freebsd-geom the steps I took to do a fresh install of FreeBSD 5.3-BETA to create an root-on-gmirror setup (http://lists.freebsd.org/pipermail/freebsd-geom/2004-September/000307.html). A similar technique could be used to gmirror an existing setup. Cheers, Paul. -- e-mail: paul@gromit.dlib.vt.edu "Without music to decorate it, time is just a bunch of boring production deadlines or dates by which bills must be paid." --- Frank Vincent Zappa