When we released JBM 2 Alpha1, we released some performance results and we thought they were already great.
I have recently spent a lot of time working on the journal, testing and improving it, making it as reliable as possible, and because of one of the improvements we achieved the Journal is at least 40% faster on persistent messages than it was on JBM 2 alpha. Depending how you configured Alpha that could mean 100% improvement.
We are aways reusing files on the journal, putting them back as fast as we can. Because of the data format we are now using we don't need to refill the file, and that saved a lot of time on I/O as records were being added on the journal.
And what's great is, we still have room for improvements in performance.
JBoss Messaging 2 rocks!