Patrick, Looking at the log files you sent I'm seeing JGroups doing a lot of retransmission of messages. Basically for each ~60K of content JGroups sends a message; if the receiver detects some messages are missing it asks for retransmission of the missing message and won't deliver messages to the application until the missing message is received. If you get a lot of that it will certainly slow things down. I'm going to assume you are using the standard JGroups configurations that ship with the AS and that the problem isn't there. Much more likely is it's an OS-level issue; OS isn't providing large enough buffers for UDP datagrams. Result is datagrams are lost at the network layer, so JGroups never sees the messages and needs to have them retransmitted. The default UDP buffer size on many OSs is very small. http://www.29west.com/docs/THPM/udp-buffer-sizing.html has a nice section on how to configure UDP buffer sizes on various OS's. The stock JBoss AS config can utilize up to a 25MB in UDP buffer, so if you have memory resources to allow that much, go for it. If not, provide as much as you can but I'd say at least 2MB. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4242467#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...