Patent ID: 8032785

Claim:
A method for use in a storage system comprising the steps of: providing a plurality of active disk drives; providing a plurality of spare disk drives to provide a maintenance-free system; spreading a logical unit of data across the plurality of active disk drives; if an active disk drive of the plurality of active disk drives fails, allocating an area on a spare disk drive of the plurality of spare disk drives to the logical unit of data and re-building the logical unit of data, the logical unit of data now being spread across the spare disk drive and the plurality of active disk drives exclusive of the failed disk drive; scheduling system maintenance visits on the storage system in a predictable manner, no maintenance being required to fix failed disk drives between scheduled maintenance visits; and deferring replacement of the active disk drive that failed until a next scheduled maintenance visit, and replacing the active disk drive that failed during the next scheduled maintenance visit; wherein scheduling system maintenance visits includes: tracking an amount of available spare space on the plurality of spare disk drives; and scheduling a next scheduled maintenance visit when the amount of available spare space on the plurality of spare disk drives falls below a fixed non-zero threshold.