I'm hoping to have a more detailed, and hopefully constructive, version of a conversation that happens on Facebook every time there's maintenance (scheduled or otherwise). What I'm hoping not to have is a meaningless argument over whether one MMO is 'better' than another, I am going to be talking about another MMO and whether ESO could use some ideas from it, but I do not think direct (or indirect) comparisons of the two or arguments over which is better are going to be relevant or constructive so if we could avoid that it would be great.

Every time ESO has maintenance there's a conversation on Facebook that goes something like this:
ESO: The X megaserver will be down for maintenance at Y time.
Person 1: Over-done 'Elder Scrolls Offline' joke.
Person 2: All MMOs have downtime for maintenance.
Person 3: Guild Wars 2 doesn't.
Person 1 & 2: This isn't GW2!

Now to my mind everyone in this conversation except person 1 is making valid points, just maybe not in the most constructive way. It is completely true that all MMOs (all servers actually) need maintenance to keep them working and that it's not possible to update a server while it's still online. However it is also true that Guild Wars 2 (and GW1) doesn't have regular downtime for maintenance and very rarely has unscheduled downtime. If I remember correctly GW2 has only gone offline for maintenance once in it's 3 year lifetime. They do carry out maintenance and add patches regularly, but when it happens players just have to restart to get the new build, so the only wait time is however long it takes to download the new build.

When players question how this is possible the usual explanation is simply that it's because they use megaservers, so one server can 'cover' for another and create the illusion that they're all online all the time. Which is what makes me wonder if it could be possible for ESO to do something similar, since it also uses megaserver technology. The part I'm unsure about is whether there is anything in common between the two other than the name used and the fact that the end result is that everyone in the same region can get into the same version of the map (but not all at the same time).

There are some long videos here which explain how GW2 does it in detail: http://www.gdcvault.com/play/1016640/Guild-Wars-2-Programming-the
And there's a Reddit AMA here which discusses it in simpler terms: https://www.reddit.com/comments/11mz4k/i_am_a_programmer_for_guild_wars_2_amaa

"So, the server (computer that hosts the game) needs to be updated! Rather than kick everybody off it and reboot the game, they keep the game going, and instead install the update on a different computer. In the future, if people try to connect, they get sent to new, updated computer! But people are allowed to keep playing on the old one, so nobody gets kicked off. Also, people can keep playing on the old one while the new one is still installing. Yay! Computers are awesome. Also, to be really sneaky, the two computers talk to each other, so they can pass messages and you can still communicate with people on the other one. This presents the illusion that the server never went down."

So, does anyone think it might be possible for ESO to do this? Does anyone know how the megaserver system actually works, other than what we can see of it while playing?