CirrAS uses cluster or group profile. What's the difference? In cluster profile sessions are replicated in whole cluster, but in group profile — not.
These profiles are nothing new – cluster profile is an alias to all and group is an alias to default JBoss AS profile.
There is also one more thing worth to notice with group profile. We're using a great Apache module mod_cluster for load balancing. In group profile there is no connection between nodes in cluster and therefore mod_cluster cannot compute load in whole cluster.
Why would I may be interested in group profile?
In some cases, there is no need to have a full session replication in a cluster, and users are fine with session lost on node failure. If you just want to have a working cluster but you're not interested in session replication — use group profile.