Optimization questions

Specs:  Server RedHat 7.1  2.4.2-2 kernal everything build with Interchange
4.8 

I am learning Linux and Postgresql from scratch.

1.  Can someone point me to or explain any linux kernal optimizations for
redhat that can made to maximize performance of a postgresql server?   I
have briefly looked at Momjian's performance recommendations for the
postgresql database itself, but I wondering if there is more that can be
done?

2.  What RAID levels does postgresql support?   I don't want to make any
assumptions.    I plan to put the data on an EMC Clariion FC4700 with RAID
10 eventually.

3.  How much memory does postgresql require?   Is there a best known method
for size of memory in relation to the size of the database and expected
growth rate?  Is there a way to optimize memory i.e. page free space and
page splitting - this may not be applicable but I have been tasked to
research it.      

4.  How is Symmetric Multiprocessing Processor (SMP) configured?   Can
postgresql take advantage of SMP? 

Thanks,
Jeff