A fascinating read about the technology stack that drove the original Ultima Online servers.
Maybe gives you an idea of what goes on behind the scenes for something like Nostalrius, the next time there's a server crash and "rollback"!
http://www.quora.com/What-was-the-techn ... rs?share=1
https://news.ycombinator.com/item?id=9818996
-Shiraz