I'm curious what kind of OS tuning was required for 500k concurrent connections. It's obvious that some ulimit tuning is necessary, but I'm wondering if any other hard limits beyond that were hit? Also, in case the original author is reading, you might find this interesting as well. It's an article on trying to reach 1MM concurrent connections with Erlang.

http://www.metabrew.com/article/a-million-user-comet-applica...