Configuration Suggestion

Hi! Here is the Specifications of My Server.
I would really appreciate the best configuration of postgresql.conf for my
sevrer.

I have tried so many value in the parameters but It seems that I cannot get
the speed I want.

OS: Redhat Linux
CPU: Dual Xeon
Memory: 6 gigabyte
PostgreSQL Version 8.0

Most of my queries are having Order by Clause, and group by clause.
Creation of temporary table.

The biggest rows is about 3-5 million which I query almost every 5 seconds.

I'm just wondering is it normal to have this result in my memory usage:
             total       used       free     shared    buffers     cached
Mem:       6192460    6172488      19972          0      39904    5890824
-/+ buffers/cache:     241760    5950700
Swap:      2096472          0    2096472

What does this mean?


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