Joao, I will explain just tell me which container (AS) and which mod_cluster first.
I'm using JBoss 5.1.0 GA, because the application that I need to deploy only supports/is certified this version or below.
The mod_cluster that I'm using is version 1.1.3 and I'm using the packed Apache distribution.
Haha, looks like a promised an answer.
In AS5 the concept of domain was used to mark a group of nodes. If a node went down, the loadbalancer would failover to a server from the same group. If there werent any other, it would failover to another domain in that case. Also session draining can be done on the whole domain, so if you have 2 racks you can shutdown 1 which is drained, so on.
In AS7 the concept of domain is used in the application server itself, so it was deprecated for better name load balancing group. Actually, the MCMP stayed backward compatible, but still https://issues.jboss.org/browse/AS7-1721
Thanks for the clarification!