Google says that yesterday morning's Gmail outage was caused by disruptions in its European data centers. The incident was triggered by unexpected issues with a software update, resulting in more than two hours of downtime for the widely used webmail service. Here's an explanation:
This morning, there was a routine maintenance event in one of our European data centers. This typically causes no disruption because accounts are simply served out of another data center. Unexpected side effects of some new code that tries to keep data geographically close to its owner caused another data center in Europe to become overloaded, and that caused cascading problems from one data center to another. It took us about an hour to get it all back under control.
Google is offering a 15-day service credit to Google Apps customers who pay to use Gmail with their domains. As background, here's some additional information on Google's European data centers. The company has purchased land in Austria and Finland to expand its data center footprint in Europe, but has made no announcements yet about whether or when it will build in these locations.