Tranquility is the only server that EVE Online needs. The system can hold a countless number of players online at once as multiple IBM blade servers work together to sustain the entire universe. Don't confuse this with instancing, like Guild Wars does with their cities and such. Players are never on different "channels" or separated by instancing of the universe. Everyone is always in the same space.
This creates both good and bad circumstances for the universe of New Eden and it's 50,000+ concurrent online inhabitants. One of EVE's more noticeable problems, thanks to the high concurrency, is the crippling lag that seems to sweep over certain systems in the universe. Jita, the trade hub solar system, is one of the beasts that the Tranquility server wrestles with each day. As more people stack in to trade with one another, the system turns into a veritable slide show at peak times. Fleet battles sometimes perform the same way, as huge groups of players enter the same system to do war with one another, however now fleet coordinators can call in computing power reinforcements thanks to EVE's fleet reservations. Declare your battle ahead of time, and CCP will make sure your system has enough computing power to resist the nuclear bomb of lag.
But the good circumstances almost always outweigh the bad when it comes to EVE's server architecture. One server means one world, and one world means all actions have an impact. This is part of what makes EVE so darn interesting to read about, as all events have the ability to change the face of the game.
Take, for example, the story we did on the GoonSwarm alliance successfully infiltrating and defeating their long time rivals, Band of Brothers. If GoonSwarm and Band of Brothers were on an EVE server that you weren't on, would you have cared as much? It wouldn't have been as much of an accomplishment if EVE was split into multiple servers. "So what if another alliance goes down, they go down all the time on my server," we may have thought.
But that act of destruction changed the flow of power and wealth in EVE. Did you know that some of the spoils of Band of Brother's gigantic budget reached down into the newbie zones thanks to GoonSwarm, as one player flew around handing large sums of money to new pilots after they stole from BoB's ISK wallet? Or did you stop to consider how many alliances would fly into the regions that use to be controlled by Band of Brothers just to get a slice of the resource pie, causing all out war and havoc?
One server that houses the entire game's population is more than just a technological feat and a feather in EVE's cap. It's a major defining factor of what makes this game so amazingly intricate and complex, and that's why you should be playing it.
[Editor's Note: We were contacted by CCP who had this to say about the lag issue mentioned in this article: "Since the release of Apocrypha 1.3 this is simply not true anymore. This was quite true before we released StacklessIO in Sep 2008 and perhaps during some big peak hours after that. But since Apocrypha 1.3 in June 2009 there is no lag in Jita."]