A study of soft error consequences in hard disk drives

Hard disk drives have multiple layers of fault tolerance mechanisms that protect against data loss. However, a few failures occasionally breach the entire set of mechanisms. To prevent such scenarios, we rely on failure prediction mechanisms to raise alarms with sufficient warning to allow the at-risk data to be copied to a safe location. A common failure prediction technique monitors the occurrence of soft errors and triggers an alarm when the soft error rate exceeds a specified threshold. This study uses data collected from a population of over 50,000 customer deployed disk drives to examine the relationship between soft errors and failures, in particular failures manifested as hard errors. The data analysis shows that soft errors alone cannot be used as a reliable predictor of hard errors. However, in those cases where soft errors do accurately predict hard errors, sufficient warning time exists for preventive actions.