Second Life and the Scalability of Online Games

The virtual world Second Life has been the beneficiary of extraordinary buzz lately. The MMORPG has had been featured in a Business Week cover story as well as favorable coverage from influential blogs. As Second Life wins fans and users, can its infrastructure scale along with its audience?

That’s what News.com is wondering in a story that looks at the backend of Second Life, in terms of both its technology and business model. Second Life differs from traditional MMORPGs such as World of Warcraft or Everquest,which run copies of the same “virtual world” on hundreds of servers,with each environment known as a “realm.” Second Life operates as agrid, with different components of its environment spread acrossmultiple servers. Here’s an excerpt from the News.com story:

“Second Life” currently runs on 2,579 servers that usethe dual-core Opteron chip produced by AMD. Each server is responsiblefor an individual “sim,” or 16 acres of virtual “Second Life” land. Atpeak usage that means that each server is handling about three users.“Most (massively multiplayer online games) have hundreds to thousandsof players per server machine,” said Michael Sellers, who runs OnlineAlchemy, a provider of artificial-intelligence tools for online games.“Is there a way they can achieve (significant) elements of scale? Ihaven’t seen that.”

Some observers of virtual worlds see challenges for Second Life asit scales beyond its current structure - which has a very low ratio ofusers to servers - and seeks to accommodate more users. Retaining thatserver-to-user ratio would be expensive.

The vulnerability of Second Life’s grid structure has been on display in several significant outages caused by in-game griefers unleashing attacksusing rapid generation of virtual objects they created using the game’stools. When a server fails in WoW or Everquest, one realm goes offline.When the Second Life grid fails, the entire game is unavailable.

While the News.com article doesn’t get deep into the nitty-gritty, Tim O’Reilly recently conducted a review of infrastructure used by Web 2.0 (sorryno trademark jokes today) companies, which included detail on SecondLife’s evolving infrastructure. Here’s a snippet from Ian Wilkes,Director of Operations and architect of Second Life’s database andasset backend:

We’ve eschewed any of the general purpose clustertechnologies (mysql cluster, various replication schemes) in favor ofexplicit data partitioning. So, we still have a central db that keepstrack of where to find what data (per-user, for instance), and Nadditional dbs that do the heavy lifting. Our feeling is that this isultimately far more scalable than black-box clustering. Right now we’restill in the transition process, so we remain vulnerable to overload.