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Re: disklabel(8) allows addressing non-existent space

On Fri, Dec 30, 2011 at 01:12:48PM -0500, Mouse wrote:
> > Btw, what do you think about alignment support for disklabel (useful
> > only for shell or interactive mode)?  With more and more 4K disks and
> > SSDs, that would be useful imho.
> Possibly.  Might be worth doing.  If you're contemplating doing it,
> though, it might be worth allowing non-zero remainders (for example,
> allow aligning to "sector number % 8 = 5"); I've seen it said that some
> disks offset their 512-byte-block interface in such ways to deal with
> certain Windows use patterns.

Unlikely, recent windows uses a much larger alignment for large disks.
Possibly 1Mbyte, I think sysinst might use the same rules.
(I remember the code going in somewhere.)

The 'problem' is that, historically, you wanted to match the physical
geometry. But since modern disks lie (and don't have fixed geometry)
and the pc bios has to use it's own (different) fake geometry there
is even a mismatch between the track/cylinder alignment rules for
the mbr partitons and the division of a single mbr partition into
multiple filesystems.


David Laight:

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