Postgres performace with large tables.

Hello All,

 I have a database with the inventory of my backbone routers. The 30
routers are stored in table.
Every 5 minutes, I insert the interface counters into a table for all
the routers.
When my table (counters_table) has less than ,let's say, 100000 records,
the insert is done within the 50 seconds for all the routers.
I noticed that, when my table contains more than 500000 records, the
insert takes about 230 seconds...

My DB runs on a Pentium III 512MB RAM and one CPU 1.13GHz

I used EXPLAIN to test my select queries, but everyting seems fine
(right use of indexes...)


How can I speed up the insert (and improve the performance).



Thanx!

Wim