Postgres Clustering Options

I'm trying to meet a very high uptime requirement in a high performance environment.

to do this we will need to have some form of cluster for our databases

What I plan on doing is:

Postgres installed on a Cluster configured in active/passive (both pointing to the same SAN
(If PG or the OS fails we trigger a failover to the passive node)

Log shipping between that cluster and a single PG Instance off site.

Is this a common/reccomended method of handling clusterin with Postgres? google searches
basically point to using a replication based solution, which i don't think would meet my
performance demands.

Does anyone have expereince with this or a similar setup that they could share with me?

Thanks

Dave