mirorring databases with small time gaps

Hi all pg admins,

    here is the problem we're encountering now. We've got a pgsql database server, logging informations (such as
alarms,week-events and so on) for a measure system. This database is mainly fed by a collect daemon which
inserts/updatevalues in tables and generates alarms (inserts). 
    The alarms are ack'ed by differents programs (Java though JDBC or python).

    The problem is that this database server only holds 7 days datas then drop then.

    A second server with more disk space, is running pg and measure and generated alarms are "inserted" into its tables
bythe daemon (duplicating inserts). 

    The problem, is that we would like to avoid to modify each client program which updates alarms (for acknoledgement)
butwe would like to sync 7 days database with the bigger one.  

    The constraint is that data difference time gap should be reduced under 5 minutes.

    So I wondered if replication server will work (but we should replicate only update/inserts not delete from the 7
daysto bigger database). What about the server load with such a replication? 
    Is there a trivial way to "log & replicate" insert/update on a given table? Do we have to modify all the client
applicationin order to make them ack alarms in 7 days database and in bigger one also? 

    By advance, thank you.

--
Jean-Christophe ARNU
s/w developer
Paratronic France