linux distro for better pg performance

Hi,

I am using pg from 3 y. and generaly I do not have big problems with it.

I am searching for best pg distro to run pg (7.4.1).
At the moment I am using RedHat AS 3.0, but I think it have some
performance problems (I am not sure).
My configuration:
P4 2.8 GHz
1 GB RAM
120 GB IDE 7200 disk.
Kernel version 2.4.21-4.EL (it is the installation vesrion for rh 3.0) .

My problems:

If I run some query with many reads, I see a massive disk transfer :
procs memory swap io
system cpu
r b swpd free buff cache si so bi bo in cs us sy
id wa
0 0 0 261724 3252 670748 0 0 0 4 105 19 0 0
100 0
0 0 0 261724 3252 670748 0 0 0 0 101 11 0 0
100 0
0 0 0 261724 3260 670748 0 0 0 4 104 19 0 0
100 0
0 1 0 259684 3268 674112 0 0 964 7 131 57 0 0
95 4
1 0 0 119408 3288 808540 0 0 27960 0 572 630 13 14
24 49
1 1 0 15896 3292 914436 0 0 7984 44744 531 275 11 18
24 47
0 2 0 16292 3296 924996 0 0 4145 6413 384 176 2
5 0 92
0 1 0 19928 3316 928844 0 0 11805 13335 497 388 5
9 5 81
0 3 0 19124 3296 924452 0 0 3153 19164 287 295 5 11
16 68
0 1 0 15956 3304 932984 0 0 536 6812 366 123 4
6 3 87
0 2 0 24956 3300 921416 0 0 1931 22936

And if I run top, I see a big iowait % (some times 70-80) and very low
user % (10-15).

I readet many docs about this problem, but do not find any solution.

My question:

If some one is using RH 3.0, pls post some result or suggestions for it
performance with pg .

What is the best linux distro for pg?

Can I get better performance by using 15K SCSI disk ?
Or it will be better to have more RAM (2 or 3 GB) ?

regards,
ivan.