The present invention provides a system, method, and computer program product for partially pre-writing data stored in an array of mass storage devices to a spare disk dedicated to the array prior to detecting a failure in the array. The system then reconstructs data from the failed disk using data partially pre-written to the spare disk. Since some of the data has already been pre-written to the spare disk, embodiments of the present invention reduce the number of I/O operations performed by a storage system during a process of reconstructing data from the failed disk to the spare disk.