Date: Tue, 24 May 2011 13:04:50 +0400 From: "Andrey V. Elsukov" <bu7cher@yandex.ru> To: Andriy Gapon <avg@FreeBSD.org> Cc: Marcel Moolenaar <xcllnt@mac.com>, Warner Losh <imp@bsdimp.com>, freebsd-geom@FreeBSD.org Subject: Re: [RFC] Remove requirement of alignment to track from MBR scheme Message-ID: <4DDB74B2.702@yandex.ru> In-Reply-To: <4DDB5375.6050004@FreeBSD.org> References: <4DDA2F0B.2040203@yandex.ru> <D75B2856-D9D8-4BA3-BC54-8258610CEA06@xcllnt.net> <9ED563AB-7B35-40F4-A33E-015317858401@bsdimp.com> <4DDB5375.6050004@FreeBSD.org>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF71682544821A7544380DDF5 Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: quoted-printable On 24.05.2011 10:43, Andriy Gapon wrote: >> On May 23, 2011, at 10:35 AM, Marcel Moolenaar wrote: >>> I think we've had enough rushed and ill thought-out changes going >>> in already and I can see that not aligning MBR partitions on a track >>> boundary is potentially perceived as a PITA violation. >=20 > _PITA_ violation? :-) > As to POLA - yeah, I can see people getting astonished that finally Fre= eBSD got > its sh*t together and did the right thing, years after all other OSes (= even > Winddows) had done it. >=20 >> I can understand only generating MBRs on a track boundary. >=20 > No. E.g. I wanted to create a 4KB aligned MBR slice, but our tools ins= isted on > using a 63 sector alignment. In fact, the value that I provided was si= lently > rounded to the value that gpart thought was best for me. > Really, if a user says to gpart "do whatever alignment you want", then = I could > see using geometry-based values, but I still think that we should not d= o that > even in that case, I think we would be better off using some nice 2^N a= lignment. > If a user says "use this alignment or slice start", then the tool shoul= d just > shut up and do exactly what the user told it. There are several operations which can/should be changed: 1. MBR detection. All users want keep their partitions accessible. But with r221788 it is now problematic. I can revert r221788, but for me it seems right and instead reverting MBR support should be changed: a) table->gpt_last should not be aligned to track boundary; b) table->gpt_first can be aligned to track for compatibility, but if there is already some partition starts from inside first track, table->gpt_first should be set to 1. 2. MBR creating. a) table->gpt_last should not be aligned to track boundary; b) table->gpt_first can be aligned to track for compatibility. 3. Creating partitions. Users should choose alignment method, not the ker= nel. and they can do it: Align to 4k: # gpart add -t freebsd -a 4k -s 5g ada0 =09 Align according to disk geometry: # gpart add -t freebsd -g -s 5g ada0 So, patch is here: http://people.freebsd.org/~ae/mbr_geometry.diff Examples: # gpart create -s mbr md0 md0 created # gpart show md0 =3D> 63 4294967232 md0 MBR (5.5T) 63 4294967232 - free - (2T) # gpart add -t freebsd -s 10g -a 4k md0 md0s1 added # gpart show md0 =3D> 63 4294967232 md0 MBR (5.5T) 63 1 - free - (512B) 64 20971520 1 freebsd (10G) 20971584 4273995711 - free - (2T) # gpart add -t freebsd -s 10g -g md0 md0s2 added # gpart show md0 =3D> 63 4294967232 md0 MBR (5.5T) 63 1 - free - (512B) 64 20971520 1 freebsd (10G) 20971584 45 - free - (22k) 20971629 20971503 2 freebsd (10G) 41943132 4253024163 - free - (2T) --=20 WBR, Andrey V. Elsukov --------------enigF71682544821A7544380DDF5 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) iQEcBAEBAgAGBQJN23S2AAoJEAHF6gQQyKF6rq0H/RRaCS8VMYqYX6kSlE/G921J PwmElExTTopQDbmf3zAQpT6W9ievyvTqSF0DmYmnthmYhbDWy9rbSBPxGsHUoofz hiTI6z/r1X+sLLHHi2awjICUnToUvlkaa2zQ4SN4x3mgUcyJ56wZsrakwitS8K7S OAX9Ra1Tz/Tp8PzN/eB2PV8bL8ohklKCMpdV/LddubKPv23nMUagxygJr8nVl+0g eUw+cy6ygyTEKuCnbx/E3IwtYeC++f5LyvNXXQm+1PGrqlfzMMKU7f/NJpzwDoX1 zDdoeI95xR8T6ycr7sJFrTcuFEr8r/wruI9oKPXOL5tq8am9dmP9RJFCqWcZAjs= =tJ5w -----END PGP SIGNATURE----- --------------enigF71682544821A7544380DDF5--
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