Google reports data loss at data centre in Belgium after lightning strike

Google said data discs at one of its data centres in Belgium have lost data after the local power grid was struck by lightning four times.

As a result, some people now faced permanent loss of access to the files on the affected discs.

A number of discs that were damaged however, later became accessible.

Data centres generally required more lightning protection than most other buildings.

According to Google, lightning did not actually strike the data centre itself, but the local power grid and according to the BBC, customers through various backup technologies, were able to recover all lost data.

While four successive strikes might sound unlikely, lightning does not need to repeatedly strike the same place or the actual building to cause damage, according to commentators.

According to Justin Gale, project manager for the lightning protection service Orion, disruptions could also be caused when lightning struck power or telecommunications cables connected to a building at a distance.

"The cabling alone can be struck anything up to a kilometre away, bring [the shock] back to the data centre and fuse everything that's in it," he told BBC.

The Google Compute Engine (GCE) service allowed Google's clients to store data and run virtual computers in the cloud. It was not known which clients were affected, or what type of data was lost.

The electricity grid powering facilities in Saint-Ghislain, near Mons suffered four successive strikes which affected 5 per cent of persistent, or non-virtual discs in the zone that powers Google Compute Engine, its cloud computing platform.

The problem was compounded with the failure of the data centre's battery backup.

Google said that the vast majority of the data was recovered between last Thursday, when the strikes occurred, and Monday.

On Friday the internet search company said only 0.1 per cent of persistent disk space had been affected, and this was reduced to 0.000001 per cent by Tuesday.

"In almost all cases the data was successfully committed to stable storage, although manual intervention was required in order to restore the systems to their normal serving state," the Google said.

"However, in a very few cases, recent writes were unrecoverable, leading to permanent data loss on the Persistent Disk. This outage is wholly Google's responsibility."