>   3	sd0: CDC Wren 6  662.6mb  (concatenated all but 1 cylinder)
>   2	sd2: CDC Wren 6  662.6mb  (concatenated all but 1 cylinder)
>   0	sd3: CDC Wren 6  662.6mb  (concatenated all but 1 cylinder)
>   5	sd5: ST12550N   2138.0mb  (concatenated all but 1 cylinder)
>   6	sd6: CDC Wren 8 1413.8mb  (concatenated all but 1 cylinder)

(sigh, really wish ccd would behave more sensibly; having to lie about
cylinder size to avoid wasting space is a pain.)

> Now if it were only possible to add partitions "on-the-fly" when one
> fills up, add another [and of course, the program that fills it up
> must not die]!  (newfs -- *sigh*)

I can't help with the while-mounted bit - for that, you need something
akin to Auspex's "isolation" notion - but I can at least avoid the need
to newfs.  I wrote a program ("fsresize") which can resize filesystems,
either grow or shrink, without losing their contents.  The filesystem
needs to be unmounted at the time - though you could probably keep it
mounted if it's mounted read-only during the update, and you mount -o
reload afterwards.

It's NetBSD-only at present (until I find enough docs on others' ffs
quirks), but for your purposes that's not a problem. :-)

source:  ftp://collatz.mcrcim.mcgill.edu/mouse/fsresize.c
manpage: ftp://collatz.mcrcim.mcgill.edu/mouse/fsresize.8

					der Mouse

			    mouse@collatz.mcrcim.mcgill.edu