Hardware optimising

Hi

I am about to upgrade a server that is about to be running a large and busy
postgresql database
currently it has

128 MB 100 MHz SDRAM
AMD K6-2/300 CPU
10 GB 7200RPM 9.0ms IBM IDE HDD

It will, over the next few months, as money becomes available, be upgraded to:

256 MB 100 MHz SDRAM
Dual Athlon 500 CPUs
10 GB UltraII Wide SCSI drive

The database will contain several million records and needs to be able to do
very fast selects from tables with a lot of rows, and do small updates and
inserts onto these tables at a good speed also.

Now, as the funds for this upgrade are trickling through slowly, I need to know
where I would see the most performance increase initially. Which of the three
peices would I be best to upgrade first to see the best performance increase. I
am leaning towards the fast scsi, as there is a LOT of data transfer.

Any insights from people that already run big databases, do we need memory, CPU
or fast disc most?

Thanx
                        M Simms
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