Office 365 Outage Affects Millions

Millions of Office 365 users were stranded by a global outage caused by DNS problems last night.

Hotmail and Skydrive services were also affected and Microsoft was still reviewing the incident this morning.

The services are reported to have gone offline around 3am for around two-and-a-half hours. The early morning timing mitigated any disruption for European users but it was in the middle of the working day for many users in America and Asia.

A posting on the Windows Live blog at 0649 GMT said: “We have completed propagating our DNS configuration changes around the world, and have restored service for most customers.  Depending on your location you may still experience issues over the next 30 minutes as the changes make their way through the network.”

Reliability issues

The latest incident follows an August outage for Office 365 in America that came just weeks after the service’s launch and raises further questions about the cloud’s reliability.

Lightning strikes cut the power to two major Amazon and Microsoft data centres and disabled backup systems in Dublin in early August, resulting in up to twelve hours of downtime for European users of some services.

And Google Docs, Google’s rival service to Office 365, also went offline for a period of around an hour this Wednesday night with access to Google Docs List affected.

Higher expectations

Downtime is always frustrating but, unlike Google Docs, users pay for Office 365 and would expect a more resilient service from Microsoft .

Just six days before the Dublin lightning strike, an article on the Daily Telegraph website said Microsoft’s Dublin data centre included a “comprehensive system of secondary electricity sources” and the whole operation could switch seamlessly to Amsterdam in the event of a “major catastrophe”. At the time Microsoft would not tell eWEEK Europe whether this system had come into play, but it appeared it did not.

The nature of Microsoft’s DNS issue in this latest outage is not clear but the system acts as the Internet’s phone book, translating human language such as eweekeurope.co.uk into machine-readable numbers.