Hi again, Steven!

Just to note that there is another actor in the play: the BSD disklabel.

Don't know how it will affect a non-ffs filesystem (or a computer
running a non-BSD operating system at all!), but it is certainly
a challenging issue for the ffs filesystem.  I have an external 80 GB
Plextor drive I want to share between NetBSD and OpenBSD.  Both
OSes have different disklabels making filesystems incompatible:

  - when making the disklabel and filesystem on OpenBSD the disk cannot
    be read on NetBSD (there is a different disk geometry).  The ffs
    filesystem cannot be mounted, and the disklabel command returns
    wrong information.

  - whem making the disklabel and filesystem on NetBSD it can be read
    and write on OpenBSD, but some tasks (e.g., check the filesystem
    integrity) could destroy the filesystem.

*Don't know* if it is an issue for ext2/3, FAT32 and other filesystems,
but it is a source of problems for ffs filesystems (ffs2 is not supported
yet in OpenBSD, but support is planned for 4.1, though).  Perhaps there
are other differences (e.g., in the superblocks) but the disklabel itself
renders the filesystems unshareable.

I would be glad to share that disk between my laptop, desktop and
Soekris net4801 computers.

Cheers,
Igor.