Yesterday's high-profile technical problems with Gmail were caused by the failure of "two separate, redundant network paths", according to Google.
The partial outage, which lasted for 10 hours on Monday, saw more than 30 percent of emails sent to Gmail accounts delayed by up to two hours and also caused severe problems for users attempting to download attachments.
Writing on Google's Enterprise blog, Gmail's senior site reliability engineering manager Sabrina Farmer insisted that what occurred was very unlikely, but nonetheless happened anyway.
"The message delivery delays were triggered by a dual network failure," she explained. "This is a very rare event in which two separate, redundant network paths both stop working at the same time. The two network failures were unrelated, but in combination they reduced Gmail's capacity to deliver messages to users, and beginning at 5.54am PST messages started piling up."
She added that Google's automated monitoring systems had immediately alerted the engineering team, which began working to solve the problem. "Together with the networking team, the Gmail team restored some of the network capacity that was lost and worked to repurpose additional capacity, clearing much of [the] accumulated message backlog by 1pm PST and the remainder by shortly before 4pm PST."
This latest outage – which follows a more significant glitch that took down Google search, Talk and Drive in August – once again raises the question of outsourcing an entire set of business processes to the cloud, especially a free service used by more than 300 million people. Google's paid-for Apps services are popular with small businesses, with affordable pricing plans coupled with powerful products and ever-improving integration with legacy systems, but the firm still has to prove that it can handle the scale of its entire portfolio.
Earlier this year, Microsoft suffered a similar problem, with its Outlook (formerly Hotmail) email services going completely offline following an overheating data centre. Microsoft is one of Google's firm rivals in the battle for the freemium cloud, so both companies will have to keep working to ensure their cloud services are reliable.
Google is outwardly demonstrating that it took the incident extremely seriously, and Farmer said changes would be made to the firm's internal practices to ensure nothing of the sort could happen again, but also highlighted that Gmail currently has a 99.9 percent uptime record, even taking into account yesterday's outage.
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