Been watching this thread with interest, being a database person first
I'm not from IBM but would strongly recommend DB2 (on Linux) for your
database needs. Check out the lack of limitations on the free (as in
beer) DB2 Express-C : http://www.software.ibm.com/data/db2/express
I've built a number of (as you describe) large high performance
using DB2. The DB2 support for Rails is good, and getting better all
time. I gave a presentation on a recent project of mine at IDUG
(International DB2 Users Group) in May : you can download this from -
As far as getting good performance is concerned, it is critical that
learn about good database design techniques. A number of books on
subject exist and if you want recommendations drop me a line (I'm in a
cafe at the moment, so can't give you titles and ISBNs).
If the design is good, the next thing you want to do is learn how to
exploit your DBMS using both SQL and extra functionality. For
if you are doing a lot of XML handling then in DB2 you'd learn
XPath / XQuery.
And (waiting for screams from Rails purists) learn when using stored
procedures will give you a performance boost !!!