>
> About 20 connection per minute.


Hi Andrew,
are you relying on a connection pool? Or are the connections created and
destroyed continuously?
In the latter then (if not using shared connections) you are costantly
creating and destroying processing generating a consistent overhead (which
ii showed by sys CPU utlization).

Two more things:
- you are indeed doing I/O: most writing. can you post some lines of iostat?
- your application can be cpu intensive. What are you doing on the
application side? What's the application supposed to do?

Best regards
Fabrizio