Google has blamed Tuesday's Gmail outage on routine maintenance in a European datacentre.
Gmail's site reliability manager, Acacio Cruise, posted an explanation for what happened on Google's blog. He said, "There was a routine maintenance event in one of our routine datacentres. This typically causes no disruption because accounts are simply served out of another datacentre."
But he added, "Unexpected side effects of some new code that tires to keep data geographically close to its owner caused another data centre in Europe to become overloaded, and that caused cascading problems from one data centre to another."
It took the company about an hour to get it back under control.
Cruise said, "The bugs have been found and fixed, and we are in the process of pushing out changes. We know how painful an outage like this is - we run Google on Gmail, so outages like this affect us the same way they affect you. We always investigate the root causes of rare outages like this one, so we can prevent similar problems in the future."