> a) It's a little silly that a disk can claim to be 100% full.  Once
>    it's up to using *all* of the bits, there aren't any more bits.
>    (This makes me worry that it may be in danger of corrupting the
>    system at that point...I seem to recall dumping a large bunch of
>    data to a small / in the past, and hitting "105%" full...)

This is probably because the amount reserved for the root user is not
included in the free disk space. If you want to adjust this, try
tunefs(8).

// Thomas