No problem. It's a 3 instance cluster. Average load is only about 10 simultaneous users per instance, though we had a max of around 45 simultaneous users per instance and that went just fine. Clearly I'm planning ahead for growth : )
I opted against a hardware load-balancer due to budget constraints and instead use Sun Java System Web Server 7 as the load balancer. SJSAS 9.0 has a load-balancer plugin which can be installed into glassfish, allowing you to setup a way cool SSL connection between the web server and the application server cluster so that the cluster DAS can automatically deploy load-balancer config changes to the webserver, rather than having to manually update the load-balancer config file and then copy it over. I've been meaning to write a blog on how I did that but haven't gotten around to it yet. I followed steps at
http://blogs.sun.com/Prashanth/entry/setting_up_load_balancing_in#Installing_Load_Balancer_Plugin but it didn't work out of the box for me so I had to modify a few things. Namely, for the life of me I could not get the SJSAS 9 installer to correctly install the load-balancer plugin into glassfish (despite that being the recommended way of installing it), so I opted for the install by hand method, which took longer and gave you more chances to screw something up, but ultimately worked.
Hope that helps.
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