https://status.cloud.google.com/incident/compute/15056#5719570367119360
tldr:
At 09:19 PDT on Thursday 13 August 2015, four successive lightning strikes on the local utilities grid that powers our European datacenter caused a brief loss of power to storage systems which host disk capacity for GCE instances in the europe-west1-b zone.
In a very small fraction of cases (less than 0.000001% of PD space in europe-west1-b), there was permanent data loss.
