I recently ran a simple performance test on my laptop (a Windows XP Dell D-810 with 2GB of memory and a single processor). I had 2 processes on the same box, each process multicasting 500 million 1K messages, for a total of 1 billion 1K messages, so 1TB of data exchanged between the 2 processes. The switch used was a simple $20 100Mbps switch. The setup (and how to run the tests yourselves) is described here.
Having the 2 processes on the same machine probably (negatively) affected the test results a bit, but my main goal was really to see whether I had any memory leaks.
Anyway the results I got were promising: the time taken was roughly 22 hours, with an average message rate of ca 10300 messages per second. The standard deviation was actually very small, and the memory used was roughly 40MB (I used -Xmx100M, which is relatively small and used a conservative (a.k.a. non aggressive flow control). Attaching jconsole to it showed that free memory stayed flat during the entire run, so I'm confident that I could run the test for a couple of billion messages and still get stable memory... The one problem with jconsole though was that it ran out of memory after ca. 600 million messages but simply restarting it helped - and this didn't affect the running test. I suspect jconsole must be storing some information in memory, and accumulating that info triggers an OOM. Guess it wasn't meant to be used for such large scale tests. I actually had started a run of 2 members where every member sent 1 billion 1K messages, for a total of 2 billion messages. But then my little daughter closed the lid on my laptop after 800 million messages whiel I was away... I guess one of the perils of working at home :-)
Stay tuned for more detailed performance numbers; we will have 8 new boxes in our Atlanta lab in January and I should have some numbers by the end of February if everything goes according to plan. Also, the Novell guys working on TCP_NIO are working on an article on performance, which they measured on a 4 node cluster, and their numbers are excellent (roughly 13000 1K messages/sec). Stay tuned !