Date: Tue, 22 Jul 2008 14:50:24 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Dag-Erling Sm??rgrav <des@des.no> Cc: Peter Jeremy <peterjeremy@optushome.com.au>, Remko Lodder <remko@freebsd.org>, src-committers@freebsd.org, "current@freebsd.org" <current@freebsd.org> Subject: Re: geom_mirror silently upgrading metadata Message-ID: <20080722125024.GE3241@garage.freebsd.pl> In-Reply-To: <86fxq2ozph.fsf@ds4.des.no> 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>
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--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 <pjd@FreeBSD.org> 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--
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