We have an App with jsp/ejb/jms that we redeploy for multiple clients. A requirement is to have failover for each .ear file - so at least two separate boxes are used to start with. So far we have two boxes and 4 .ears to deploy.

Our theory is to set up a single JBoss instance on each machine and configure for failover - then to deploy the same .ear multiple times - as opposed to setting up four JBoss instances on each box and deploying a single ear on each pair.

So far it makes sense to us - but am wondering about scalability. What to do when there are 10 ears to deploy on 5 machines, or 20 ears to deploy on 10 machines?

Should we set up separate clusters with 2-3 ears each or one big cluster and just farm out 10 ears.

Obviously much of this depends on hardware and our implementation - just trying to get some ideas from others who have similiar scaling needs and what techniques they are using.

Thoughts anyone?