The missionserver, as its called, is a separate piece of software that stores the mission data as created by players. It does use some resources, but that part is not a big deal. Once you start an AE mission, it's loaded in a mapserver, like any other mission. They are not treated any differently.
The problem is that players can build missions that are a lot more resource-intensive than normal missions from the game. When enemies spawn in normal missions, most of them have their AI in an "idle" state until they are aggroed, which doesn't require much processing power. But most AE farms rely heavily on ambushes or patrols, which spawn the critters with fully active AI. And that's the problem.
Missions are run on 9 servers with a total of 224 cores. For the most part you can run lots of zones and missions on a single core without a problem; but AE farms tend to max out a core all for themselves. If there's just 100 AE AI-intensive farms running, that eats half of the mapserver processing power for all 4 shards.
Fascinating.
Do we have any info on how NCSoft handled this? I can't believe they were just throwing money at the problem over and over instead of figuring out a way of making the AI requirements from AE missions draw on elastic resources...
If I'm remembering right, the way NC dealt with the problem was removing the missions when they found them. No farming missions, no problem. Of course, they weren't transparent about WHY they were so against farming, but at this point, I'm guessing it's because the farms were taxing their server cpus.
Didn't just lead to people having their farm missions unpublished when not in use? I vaguely recall a couple of ticket farms that would appear/disappear at random times which seemed to mean someone was just publishing it when they needed. Maybe I am wrong and the guy just uploaded it each time they played and let the thing get deleted, but I do remember the same couple of farms with the same "description" appearing and disappearing.