"PostgreSQL 9.1 is now available in beta, introducing a number
of new features. Among the new features is support for synchronous
replication for the database.
In the beta there is also something called
transaction-controlled synchronous replication, which provides
control over what is and isn't replicated.
"What that means is the database administrator can decide on a
per-transaction basis which ones need to be replicated and which
ones don't," Josh Berkus of the PostgreSQL core team said. "The
advantage of that is that there are a lot of mixed load
applications which might have a small amount of essential data and
a large amount of data that is not as important."