This presentation answer a lot of your questions about PostgreSQL and the Red Hat Cluster Suite.
It reviews how you can create failover/standby capabilities with the following activities:
General PostgreSQL clustering options
Overview of Red Hat Cluster Service
Identification of candidate databases for clustering
Identification of hardware for clustering
Analysis of uptime requirements and data latency
Implementation of clustering
Testing of clustering
PostgreSQL installation tips for RHCS
Clipping is a handy way to collect important slides you want to go back to later.