Neil Harris wrote:

Oh, one last thing:

Looking at the recent Alexa traffic graphs reminded me of the recent E-mail to Wikitech-l, telling the developers that the Wikipedia infrastructure was (and I quote)

"U N S C A L A B L E"

I think that should now read "unscalable, apart from the ever-improving performance and continued exponential growth in load", or something?

I wasn't reading wikitech-l at that time, I had to look up the archives to find out what you were talking about. I for one was originally worried about the lack of scalability inherent in MySQL, but those fears seem to have been unfounded. Any of our database servers can keep up with Wikipedia's write load several times over, and we've been able to distribute the read load effectively to maintain good performance. Growing at this rate, Wikipedia will see market saturation within the next year or two, and I'm confident we won't hit a performance brick wall before then.

By the way, what _has_ caused the recent traffic spike? Added hardware? Software improvements? Better load-balancing? Something else?

According to [[Wikipedia:Announcements]] for April 2:

"Traffic continues to skyrocket, with Wikipedia's daily Alexa ranking peaking at a daily rank of 89 and a weekly average rank of 97. Several key placements on search engines have aided in the encyclopedia's popularity, such as #2 for online poker, #3 for Terri Schiavo, and #9 for Pope John Paul II."

Since then we've been given special placement in Google's definition and Q&A services, and better placement in Yahoo. The timing of this increase in demand was fortuitous, since we solved some performance problems at about the same time -- we took load off the image server (albert) by moving backups to benet and implementing a metadata cache, and we added another perlbal server, which seemed to be a bottleneck. Domas deserves special credit, for analysing our performance problems, fixing some of them and providing excellent advice on how to fix others.

-- Tim Starling