svn commit: r216269 - head/sys/geom/part

[Bruce Evans]

On Wed, 8 Dec 2010, Andriy Gapon wrote:

> on 08/12/2010 01:11 Matthew Jacob said the following:
>> Geometry is still important.  Trying booting a USB flash drive on all BIOS' with
>> a 63/255 geometry instead of a 64/32 geometry.
>
> Well, I don't know anything about USB...
> My point about modern HDDs still stands.

Hmm, I know how to avoid geometry errors in FreeBSD, but recently had
them for Linux, and had problems booting USB drives, which I didn't know
might be caused by geometry.  One USB drive has the manufacturer's
partitioning, which has starting CHS consistent with H=any/C=44 and
ending CHS consistent with H=255/S=63.  cam gives the default fake
geometry of H=255/S=63, and my de-GEOMed kernel doesn't change this
since it is consistent enough with the partitioning.  This drive is
not bootable and I haven't noticed any problems with it.  Another
USB drive has all partitions configured using the cam default.  It
boots on some systems only, almost never on one except IIRC it once
booted on that too, when the partitioning may have been simpler.

Bruce