Date: Thu, 6 Apr 2006 10:12:13 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Mike Jakubik <mikej@rogers.com> Cc: stable@freebsd.org, Eric Anderson <anderson@centtech.com>, Craig Boston <craig@feniz.gank.org> Subject: Re: gmirror on existing filesystem (was Fresh install on gmirror'ed disks?) Message-ID: <20060406081213.GA5578@garage.freebsd.pl> In-Reply-To: <4432EA5E.3060003@rogers.com> References: <440D74B3.3030309@vwsoft.com> <200603070939.30032.joao@matik.com.br> <54559.192.168.0.10.1141751042.squirrel@webmail.sd73.bc.ca> <20060316160813.GA15720@nowhere> <442033A2.2030208@rogers.com> <442043D0.6090206@centtech.com> <4432EA5E.3060003@rogers.com>
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--NzB8fVQJ5HfG6fxh Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Apr 04, 2006 at 05:51:26PM -0400, Mike Jakubik wrote: +> >>>Can someone with knowledge of the UFS internals please confirm one way +> >>>or the other if this is dangerous or not? +> >>> =20 +> >> +> >>I'm curious to know this as well, as i have some systems using gmirror= , that were setup in this fashion. Could someone knowledgeable on the matte= r shed some light? +> > +> > +> >I've gmirrored existing disks/slices before, and it's worked fine. I'm= not 100% certain about all cases, but it's possible that the filesystem co= uld be right up against=20 +> >the last block of the partition, and it could get stomped on I suppose. +> > +> >I'm not sure what this command tells you for sure, but it dumps the las= t block of a slice, or disk, or whatever: +> > +> > +> >dd if=3D/dev/ad0s3a iseek=3D`diskinfo ad0s3a | perl -ne '@d =3D split; = print ($d[2]/$d[1] - 1)'` count=3D512 | hexdump +>=20 +> Could someone provide an authoritative answer to this please? Pawel, it = would be nice to see some support for your own code from you. This is a ver= y easy method to create a=20 +> mirror on an existing system, but if its going to cause problems then it= s useless (All the more reason for geom enabled installer). I can't give you an authoritative answer, because I don't know UFS internals so well. All I know is that it (UFS) thinks the last sector is available and may want to use it at some point getting EIO then. I'm not using this method, but I've heard of many people using it without problems. Speaking about installer. I don't think I'll be able to add configuration of my GEOM classes to the sysinstall in the near future (and I hope never - I'd prefer to wait for a new installer). One can still see how many sectors exactly has the partition he is going to create file system on and add additional newfs(8) flag '-s <sectors-1>'. --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --NzB8fVQJ5HfG6fxh Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFENM1dForvXbEpPzQRAnLcAJ9OvO17F9jmwCuRZqWwgT7RjpDthQCfemwB E8GLBVAOHMsU1UZXASauYsk= =ERHb -----END PGP SIGNATURE----- --NzB8fVQJ5HfG6fxh--
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