Wikipedia was offline for nearly twelve hours today, starting about 11:00am EDT. According to Wikipedia’s Twitter feed:

“Thanks for being patient, everyone. We’ve figured out the problem: power outage in our Florida data center. Slowly coming back online!”

This is not the first time that Wikimedia has experienced problems cause by power outages. In March 2010, Wikipedia was also knocked offline globally:

“Due to an overheating problem in our European data center many of our servers turned off to protect themselves. As this impacted all Wikipedia and other projects access from European users, we were forced to move all user traffic to our Florida cluster, for which we have a standard quick failover procedure in place, that changes our DNS entries. However, shortly after we did this failover switch, it turned out that this failover mechanism was now broken, causing the DNS resolution of Wikimedia sites to stop working globally. This problem was quickly resolved, but unfortunately it may take up to an hour before access is restored for everyone, due to caching effects.”

It looks like there are still failover problems.