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Date:      Tue, 24 May 2011 23:18:52 +0400
From:      "Andrey V. Elsukov" <bu7cher@yandex.ru>
To:        Marcel Moolenaar <xcllnt@mac.com>
Cc:        Andriy Gapon <avg@FreeBSD.org>, Warner Losh <imp@bsdimp.com>, freebsd-geom@FreeBSD.org
Subject:   Re: [RFC] Remove requirement of alignment to track from MBR scheme
Message-ID:  <4DDC049C.7070904@yandex.ru>
In-Reply-To: <9B250685-62F2-4AF7-BDCC-D176FA3C6FCD@mac.com>
References:  <4DDA2F0B.2040203@yandex.ru> <D75B2856-D9D8-4BA3-BC54-8258610CEA06@xcllnt.net> <9ED563AB-7B35-40F4-A33E-015317858401@bsdimp.com> <4DDB5375.6050004@FreeBSD.org> <D7C4124D-A690-4960-B141-594C7E2BE792@mac.com> <2FCA1E3C-E11C-46C9-A41B-E5DF4D8BA1FC@bsdimp.com> <9B250685-62F2-4AF7-BDCC-D176FA3C6FCD@mac.com>

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On 24.05.2011 22:12, Marcel Moolenaar wrote:
>=20
> On May 24, 2011, at 10:46 AM, Warner Losh wrote:
>>> All I'm saying: be careful.
>>
>> Agreed.  But the care should be on the creation side, not on the inter=
pretation side.
>=20
> ... as the original code was. We just need to add a sanity
> check to the interpretation that filters out the real bogus
> information (resulting in a partition with negative size).

A partition with negative size is not the one problem.
Some time ago i found an easy reproducible bug, when BSD scheme
creates providers with size bigger than parent provider size.
Also  there was nothing against creation of overlapped partitions.

> With respect to the creation:
>=20
> Since out synthesized geometry is not necessarily the same
> as other OSes, we could opt to synthesize a geometry that
> has a track size (=3D sectors/track) that is a multiple of 8
> (to play nice with 4K sectors), and/or take the stripe
> size of the underlying GEOM into account. This fundamentally
> doesn't change a thing for MBR, but has the side effect of
> achieving some of the goals *and* automatically works for
> EBR as well.

Today's devices do not report about their 4k sectors.

> Thus: rather than hack MBR and forgetting about EBR and other

I do not forget about EBR, PC98 and VTOC8. But we need begin from somethi=
ng.

> schemes, maybe we only have to tweak the geometry synthesis
> to give people what they want without going over board. After
> 9.0 branched, we can do a lot more knowing we have plenty
> of soak time...

Ok, i can revert all related changes and just do nothing :)
It seems it is better solution :)

--=20
WBR, Andrey V. Elsukov


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