I wonder why our performance is so much worse for JBM than JBossMQ with UIL2, compared to your tests. There isn't a lot of tuning parameters I can think of. Can you? The JMS code is the same, we just change the jars. I wonder if we have a code issue that JBM is exposing but that JBossMQ is fine with. I switched back to JBossMQ and then, as you said, the persistence is the bottleneck. When the Queue grows, the server load is increasing rapidly. MySQL process is eating the CPU. The JMS client delivers the messages really fast. With JBM the Queue dosen't grow. It seems like the JMS client can't send messages fast enough. The MDB (consumer) can easily deal with the load. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4076346#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...