Gmail users who suddenly found their inboxes wiped clean on Friday can look forward to their emails being restored as Google has assured them that many of these missing emails are stored on offline tapes and efforts are on to restore these to the users' accounts.

Writing on the official Gmail blog, Ben Treynor, VP Engineering and site reliability czar has said that although Google stores multiple copies of data on multiple data centers, certain software bugs can affect several copies of the data. In this case a bug introduced by a new storage software update was responsible for deleting several copies of emails. 

However, Treynor clarifies: To protect your information from these unusual bugs, we also back it up to tape. Since the tapes are offline, they're protected from such software bugs. But restoring data from them also takes longer than transferring your requests to another data center, which is why it's taken us hours to get the email back instead of milliseconds.

About 0.02 percent of Gmail users were affected in the incident, but given the huge base of account holders it implies that the scale of the outage has been huge. The latest update on the Google Apps Status Dashboard says that access has been restored for one third of users and all who have been affected would have the issue sorted within 12 hours.

Meanwhile, Alex Chitu - writer of a blog tracking Google's cloud computing initiatives - is quoted by the BBC as saying that many users have expressed strong displeasure at the way Google has handled the issue and communicated with those affected.