CRN reports that in mid-August four lightning bolts hit the power grid supplying Google’s “ultra-energy-efficient” data center outside of St. Ghislain, Belgium. The hits caused data loss on “a tiny fraction” of data. Google said that virtually all of the data was restored. The story did not say that the restoration of total.
The story provides a lot of commentary on what might have happened but, due to Google’s penchant for secrecy, couldn’t provide any definitive answers. The commentary points to the likelihood that backup systems didn’t catch the data center load after the lightening hit. A possible failure point was the Transient Voltage Surge Suppressor. The theory is that one of the early bolts took out the surge protector, enabling subsequent bolts to cause the damage that momentarily cut power and led to the data loss.