Jboss on +cluster

My question is about JBOSS Operation Network and HA.

My HA solution (Own portal and JBOSS ON portal installed in the same machine) related with HA is to use Redhat cluster instead of JBOSS one. But i'm having some problems about this....
My doubt is:

--- Which are the differences between use JBOSS or RHCS with JON?
--- Which is the best solution?
--- Maybe it's necessary to install different cluster solution depends on AGENT or SERVER (JON) .... isn't it?
--- Any document or URL that explains how to install the best solution?

Thanks in advance.