The Google Cloud Platform center in Belgium lost some data after four consecutive lightning strikes occurred, the company reported Wednesday.
The strikes affected the Google Computer Engine (GCE) service, which allows clients to store data and run virtual computers in the cloud. Google did not report on which clients were affected or the type of data lost.
Some 5% of disks in Google's Europe-west1-b cloud zone had at least one issue with reading or writing data after the lightning strike. Engineers tried to recover the data, attempting everything from complicated protocols to simply rebooting servers, and ended up restoring everything except 0.000001% of disk space, according to Google
An automatic auxiliary system restored power quickly -- the storage systems are designed with battery backup. Some recently written data was located on storage systems that were more susceptible to power failure from extended or repeated battery drain. Manual intervention was required to restore the systems to its normal state, but in very few cases recent writes were unrecoverable, leading to permanent data loss.
"In these cases, full recovery is not possible," Google wrote in a status update.
Google called the situation an "exceptional incident," but it also took responsibility for the outage. The company continually conducts audits to determine what goes wrong in rare instances within its backup power systems and said it plans to upgrade its equipment. Read failures are more common, but infrequent.