From owner-freebsd-current@FreeBSD.ORG Tue Jul 22 12:50:25 2008 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 83D121065674; Tue, 22 Jul 2008 12:50:25 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: from mail.garage.freebsd.pl (chello087206045140.chello.pl [87.206.45.140]) by mx1.freebsd.org (Postfix) with ESMTP id D50188FC2F; Tue, 22 Jul 2008 12:50:24 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: by mail.garage.freebsd.pl (Postfix, from userid 65534) id D61BB45C89; Tue, 22 Jul 2008 14:50:22 +0200 (CEST) Received: from localhost (pjd.wheel.pl [10.0.1.1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.garage.freebsd.pl (Postfix) with ESMTP id 29B5F45B26; Tue, 22 Jul 2008 14:50:19 +0200 (CEST) Date: Tue, 22 Jul 2008 14:50:24 +0200 From: Pawel Jakub Dawidek To: Dag-Erling Sm??rgrav Message-ID: <20080722125024.GE3241@garage.freebsd.pl> References: <200807131153.m6DBrDkX067657@repoman.freebsd.org> <487C6A86.20508@FreeBSD.org> <20080715095139.GA62764@server.vk2pj.dyndns.org> <20080718070624.GC1976@garage.freebsd.pl> <86fxq2ozph.fsf@ds4.des.no> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ILuaRSyQpoVaJ1HG" Content-Disposition: inline In-Reply-To: <86fxq2ozph.fsf@ds4.des.no> User-Agent: Mutt/1.4.2.3i X-PGP-Key-URL: http://people.freebsd.org/~pjd/pjd.asc X-OS: FreeBSD 8.0-CURRENT i386 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mail.garage.freebsd.pl X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.0.4 Cc: Peter Jeremy , Remko Lodder , src-committers@freebsd.org, "current@freebsd.org" Subject: Re: geom_mirror silently upgrading metadata X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 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: Tue, 22 Jul 2008 12:50:25 -0000 --ILuaRSyQpoVaJ1HG Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jul 22, 2008 at 02:44:42PM +0200, Dag-Erling Sm??rgrav wrote: > Pawel Jakub Dawidek writes: > > Just to be clear. I fully agree with you guys. What I could do about > > that when I was working on gmirror (starting from the simplest > > solution): > > > > 1. Skip disks which have version lower then what we have in the kernel. > > > > 2. Upgrade the on-disk metadata automatically. > > > > 3. Make gmirror kernel module to work with all the previous versions and > > add 'gmirror upgrade' command, so one can upgrade on-disk metadata. >=20 > 4. Allow an older mirror to be accessed r/o by a newer kernel, side- > stepping the issue of converting metadata back to the old format. > Require an explicit 'gmirror upgrade' to upgrade the metadata and > allow r/w access. >=20 > IIRC, this is what ZFS does. I believe it would be a good compromise > between 2 and 3. ZFS does exactly 3. What you are suggesting could be done by not loading geom_mirror.ko module and mounting file system read-only from one of the mirror components. Of course automatic gmirror metadata upgrade is in most of the cases a surprise. Although, one can still just boot it on an older system and create mirror once again - 'gmirror label' command won't touch the data. --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --ILuaRSyQpoVaJ1HG Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQFIhdePForvXbEpPzQRAnUNAJ98KeRKc3WocUSWBQGnfNH85LadtQCg9Eay zz2kiky+kTZjE6w5gxb0pFs= =3ZyY -----END PGP SIGNATURE----- --ILuaRSyQpoVaJ1HG--