Google has restored access to email for around 40,000 customers whose accounts were mistakenly wiped clean this past Sunday. It says the delay in sorting the problem was because it had to restore from a physical back-up.

The problem began on Sunday afternoon when some customers found either they were unable to access their Gmail accounts, or that the accounts appeared as if they were open. That is to say, there were no messages whatsoever in the archive, except for a welcome message from Google.

Google said it was working on the problem and noted that in cases where users were unable to log-in, the company was actively working on the account at that moment.

Software Bug, Not Physical Fault

Google has now explained that the problem was a bug in a new software update to the service, which proved more troublesome than a simple technical error. The company intentionally keeps multiple copies of messages on different servers in different locations so that one physical failure doesn't affect the entire system.

In this case, the software bug affected all copies of the messages and accounts at the same time, causing the apparent wipeout.

Fortunately, Google also makes regular backups of the entire system onto magnetic tape, which is how it restored the messages.

Tiny Proportion Still Equals Big Numbers

The proportion of people affected has been revised down by Google several times, from 0.29% to 0.08% to a final figure of 0.02%. Given the number of people who use Gmail, that's the difference between 500,000 to 40,000 possibly affected users. (Source: bbc.co.uk)

Google has now cancelled the software update until the bug can be isolated. It appears those who were affected were simply unlucky enough to be first in line when the update process began.

It's still possible some messages may have been lost because they were sent after the physical back-up that was used for the restoration. However, Google notes that anything sent to an affected account from Sunday evening onwards will have been bounced back to the sender with a non-delivery notification. (Source: blogspot.com)