A developerWorks article published today provides a nice summary of IDS replication features. Replication technologies in Informix Dynamic Server by IDS engineers Madison Pruet, Nagaraju Inturi and Nick Geib, takes the reader through Enterprise Replication (ER) and High Availability Clustering, namely Shared Disk (SD) secondary servers, High-Availability Data Replication (HDR), and Remote Standalone (RS) secondary servers.
What I like about this article is that each technology is introduced with a simple example of setting it up, so as a quick start summary it works very well.
One link I would add to the list of resources at the end of the article is the Informix Dynamic Server 11: Extending Availability and Replication RedBook which is an excellent way to follow up and learn more about the topics introduced here.
Replication technologies in Informix Dynamic Server - dw Article