As I was watching my husband try and fix a raid array that had been set up
by someone in a hurry where the file
system was corrupted because two of the partitions on the disk overlapped, I
wondered why partition overlapping was
allowed. I realized that there is by definition, one large partition that
overlaps the whole disk, but why are other partitions allowed to overlap?

This was the historical answer as I understand it:
Disk partitioning used to be defined in the kernel with several different
schemes set up that you could choose from, and so the partitions needed to
be able to overlap. (I'm still not sure that this makes sense, since if you
combine two different schemes where the partitions overlap, you are *still*
going to get a corrupted file system.)

I know that if you go through install programs (i.e. freebsd, open etc ad
nauseum) that overlapping partitions are not allowed. Are there any
situations where people need to have overlapping partitions? If not, why are
we still allowing users to do that? I know that Unix in general is of the
opinion that more flexibility at the expense of protecting users from
themselves is a good thing, but it would seem downright silly to have a gun
lying around if there is nothing to shoot with it but yourself... (and you
want to live...)

Carrie Jones

"I would rather be evil than dull."     --Amy Haas