2 computers 1hd 2 postgres daemons. Is it possible?

Hi men :-)
Just one question for those of you who have spent many time with postgres.
I want to create a load balancing and High Availability system with two
servers.
This two server have a common hard disk: A RAID 5 server connected to them
by the LAN.
I have a hardware machine (WSD+ from RADWARE) that manages the load
balancing.
I want to have, two servers, and two postgres installations, one in each
server, but with a common PGDATA directory in the RAID.
So, if one of the servers crashes, people can still get the information from
the other server.
Esentially, what I want is, two postgres (one in each machine) with a shared
PGDATA directory, and that both postgres can access and do Inserts in the
tables, and when one postgres does an insert, the second sees what the first
has inserted.

Thanks.