A software error has caused further problems for Amazon Web Services (AWS) customers after data was accidently deleted as part of a storage back-up, adding to a power outage that brought services down earlier in the week.
When backing up on a snapshot, which makes a read-only copy of data frozen at a scheduled time, some blocks of Amazon Elastic Block Storage (EBS) snapshots were incorrectly deleted due to a software bug.
In a statement on its website, Amazon said: "Separately, and independent from the power issue in the affected availability zone, we've discovered an error in the EBS software that cleans up unused snapshots. During a recent run of this EBS software in the EU-West region, one or more blocks in a number of EBS snapshots were incorrectly deleted. The root cause was a software error that caused the snapshot references to a subset of blocks to be missed during the reference counting process."
Amazon said it has addressed the error and disabled all snapshots containing missing blocks. It urged users to try running the Unix file system checking tool, fsck. "In some cases [fsck] may restore normal volume operation," it said, but some users may find they are unable to restore the lost data.
Amazon will e-mail affected customers as soon as it has the copy of their snapshot available.
Amazon and Microsoft European cloud services were down at the weekend after a lightning strike caused power failures at their datacentres in Dublin.
The lightning strike took out the main power supply and affected part of the phase control system that synchronises the back-up generator plant, causing a disruption to service of Amazon's Elastic Compute Cloud (EC2) cloud computing platform for the second time this year, as well as affecting Microsoft's Business Productivity Online Suite (BPOS).