Date: Wed, 27 Jun 2012 16:08:17 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers <freebsd-hackers@freebsd.org>, "Andrey V. Elsukov" <bu7cher@yandex.ru>, Andriy Gapon <avg@freebsd.org>, freebsd-current <freebsd-current@freebsd.org> Subject: Re: [CFC/CFT] large changes in the loader(8) code Message-ID: <20120627140817.GC1372@garage.freebsd.pl> In-Reply-To: <201206270822.25672.jhb@freebsd.org> References: <4FE9B01C.30306@yandex.ru> <201206261337.11741.jhb@freebsd.org> <20120626212308.GE1399@garage.freebsd.pl> <201206270822.25672.jhb@freebsd.org>
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--sHrvAb52M6C8blB9 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 27, 2012 at 08:22:25AM -0400, John Baldwin wrote: > > I don't think so. Most common case is to configure partitions on top of > > a mirror. Mirroring partitions is less common. Mostly because of > > hardware RAIDs being popular. You don't expect hardware RAID vendor to > > mirror partitions. Partition editors for other OS's won't work, but only > > because they don't support gmirror. If they wouldn't recognize and > > support some hardware (or pseudo-hardware) RAIDs there will be the same > > problem. >=20 > Hardware RAIDs hide the metadata from the disk that the BIOS (and disk > editors) see. Thus, putting a GPT on a hardware RAID volume works fine > as the logical volume is always seen by all OS's consistently. [...] Only if you won't connect this disk to a different controller. > [...] The same > is even true of the "software" RAID that graid supports since the metadata > is defined by the vendor and thus the logical volume is always seen other > OS's consistently. But is it seen without metadata by the boot loader? What I'm trying to say is that it is fair to expect from the user to not use gmirror-configured disk on different OS. If the user wants to use this disk in different OS then he has to use format that is recognized by both. Because gmirror is supported by FreeBSD we should improve the support by teaching boot loader about it. Pretending gmirror is special and recommending to mirror partitions with it instead of raw disks is not the solution. I really can't see how gmirror is different in this regard from any other software RAID or volume manager. If you try to use disk that contains unrecognized metadata the behaviour is undefined (but hopefully not a panic). --=20 Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://tupytaj.pl --sHrvAb52M6C8blB9 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iEYEARECAAYFAk/rE9EACgkQForvXbEpPzR3+gCg0WjbLvmRZAjPToMtNypIRg9M Pp0An0JP9JJkZp5Az6GiKR0KxzbaXXG/ =N78o -----END PGP SIGNATURE----- --sHrvAb52M6C8blB9--
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