disk usage advice needed

Hello

My data directory is like (pg 7.1 linux 2.4.4)
---
$ ls
PG_VERSION  base/  global/  pg_hba.conf  pg_ident.conf  pg_xlog/  postgresql.conf  postmaster.opts
----

With 7.0.3 I remember?? that there are files named according to table
names.  With 7.1 I don't know which disk file is associated with
which table.  What I would like to do is spread the files between
two ide disks in order to gain some performance.  I heard
somewhere that I can symlink some of the files to a different
disk to gain some speed and I was wondering of which of those
files are my tables.   What advise would you give if I
can split pg data between two disks.

I think all of the data is in base/ directory and it looks
like this 

	1/  18719/  18836/  573216/

I have two currently two big tables that are
constantly (1-5 times per second the whole day)
being accessed and always simultaneously and 
I wish these two tables to live on two separately.

Thanks in advance