Google blames bug for Gmail deletions

Offline backup used to restore nuked profiles

Google has blamed problems with a storage software update for a glitch that deleted an estimated 40,000 Gmail accounts.

The snafu meant that affected users lost access to their archive of emails, contacts and IM chats. Initially Google said the glitch might have affected 0.29 per cent of its user base but this figure has steadily been revised downwards towards the latest figure, 0.02 per cent of the Gmail userbase, or 40,000 accounts. Updates to Google's App status dashboard late on Monday promise that the problem will be resolved with the restoration of deleted accounts for affected users within a matter of hours.

We have revised downward our estimate of the total number of users affected by this issue from 0.08 per cent to 0.02 per cent of Google Mail users. Access has been restored for one third of the affected users. The remaining 0.013 per cent of accounts are being restored on an ongoing basis, and we expect the issue to be resolved for everyone within 12 hours.

In a blog post, Ben Treynor, Google VP of engineering and site reliability, apologised for the cock-up and promised the prompt restoration of "deleted" accounts.

"The good news is that email was never lost and we've restored access for many of those affected," Treynor writes. "Though it may take longer than we originally expected, we're making good progress and things should be back to normal for everyone soon."

Google applies an architecture featuring data mirroring and redundancy but even so "software bugs can affect several copies of the data". The severity of the mix-up in this case means that some affected accounts will have to be restored from offline backup tapes, a time consuming process that means the exercise will take longer than Google first anticipated.

The online ad giant doesn't say this but the use of off offline backups means that its likely the most recent emails on affected accounts will be lost. It does say that emails sent to affected users between Sunday evening and Monday afternoon would have bounced.

Google has reverted to an older version of its storage software in order to safeguard against a repetition of the snafu, which has served to illustrate the point that cloud-based services are by no means immune from back-up and data loss problems. ®