> I think that you're just coming up against the limitations of the 
> standard UNIX dbm.  Try 'gdbm' instead, or 'bdb' or maybe 'cdb' 
> from the Ruby application archive.

I'd reccommend bdb over gdbm or cdb. Of course I'd recommend
mysql over any of those... and yes postgresql guys, I realize that
you don't think highly of mysql. I don't want to start a flame-war
so also check out postgresql.  :-)

One dbms that I don't have any experience with is kdb: http://www.kx.com/
and I don't think there are any ruby bindings for it.  But it does
look *very* hot for data analysis systems.  It's not cheap though...
the quote I got was:

pricing per cpu.
$40,000 min
$20,000 each additional cpu

Sorry for getting a bit OT, just in a rambling mood.

regards,
-joe