Does this question relate to JBoss Portal, or are you asking about JBoss Application Server?
Why would you expect a 40% performance improvement? My team has done a lot of testing with AS 4.0.5 on various platforms with various databases and the performance differences between JBoss AS running on Windows and on Linux have been minuscule.
We have a client that has high exportations that Linux will perform better.
From your experience, what can we expect. and What can we recommend to the client around Linux and Jboss AS. From testing that we have carried out to date there has been some big performance improvements on some sides, but not over all.
Can you possibly send me some test data and reports, this will help me a lot with the client I have.
Some pointers to help you decide:
You can get some idea from this blog: http://blog.jboss-portal.org/2008/09/scaling-jboss-portal-to-new-height.html regarding EPP performance.
Also see the http://andrigoss.blogspot.com/2008/02/jvm-performance-tuning.html
All of these were done on RHEL and JBoss EAP (Enterprise Application Platform) and JBoss EPP (Enterprise Portal Platform).
thanks for the feed back much appreciated