where is the database physically

Hi. Thank you all for your thoughful comments, Philo and Jeremy. One question
wasn't addressed (mixed in with the mess of comments, my fault...).

Where is the database located physically - i guess /var/lib/pgsql but how is
it broken into files. For instance in mysql, i find the directory
/var/lib/mysql has subdirectories labled for the databases and with files in
the corresponding directories "representing" the tables in the database. I
know that postgresql is more sophisticated, but how does it store those
tables and databases?

Why would I want to know? I just copied a huge amount of data to a postgresql
database - some tables have as more than 500,000 entries. Now I need to
monitor the size of this database as it fills the harddrive.
For instance, the default install appears to be in the /var directory ( by
looking at the output of df, i happen to have a separate partition mounted as
/var, which agrees with the postgres user having the /var/lib/pgsql as her
home. If it was not a separate partition, i might have trouble sorting out
the growth of teh database from the growth of the files on my computer.

Another reason to look at the files is to guess how much space to expect the
backup files will take up, when i do my backups (like in the next few days).
I just havent found the answer in the documentation.
Thanks you all. The program is just amazing.

Yes it was funny that my last posting had don't kill the postman on the
bottom. I promise i had nothing to do with it! :).

MItchell