Very large database

I need some help here.  We need to implement a 180+GB database with
120+MB of updates every evening.  Rather than purchasing the big iron,
we would like to use postgres running over Linux 2.4.x as the data
server.  Is this even possible?  Who has the largest database out there
and what does it run on?

How should we implement the disk array?  Should we purchase a hardware
RAID card or should we use the software RAID capabilities in Linux 2.4?
  Should we consider a SMP system?  Should we use an outboard RAID box
(like RaidZone)?

If anyone out there has implemented a database of this size then I would
like to correspond with you.

Thanks for your help,
Mike