I did a bit more testing, and it seems that once I shut down n1, there is some increase in HashMap$Entry's and TreeMap$Entry's on n2. This is a test setup, so n2 is not servicing any requests when I stop n1. So I am guessing, it might have to do with the session being promoted from backup to active, as you suggested. Could you point me to the relevant code in JBoss so I can verify? (I want to check where those map entries are instantiated) View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4258339#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...