[RFC] Remove requirement of alignment to track from MBR scheme

[Marcel Moolenaar]

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 interpretation side.

... 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).

With respect to the creation:

Since out synthesized geometry is not necessarily the same
as other OSes, we could opt to synthesize a geometry that
has a track size (= 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.

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

-- 
Marcel Moolenaar
xcllnt at mac.com