Apparatus and method for managing data in a multi-device storage system, such as a RAID (redundant array of independent discs) system. Distributed data sets are stored across a plurality of storage devices. A selected storage device is replaced with a new storage device responsive to an anomalous event. A rebuild operation is performed to reconstruct data from the selected storage device to the new storage device. The rebuild process includes accessing a list of distributed data sets in a local memory. For each distributed data set in the list identified as constituting valid data, read commands are issued to the remaining storage devices and a write command is issued to the new storage device. For each distributed data set in the list identified as constituting unused data, a data clear command is issued to each of the remaining storage devices and to the new storage device.