A control device configured to control a storage device includes a memory and a processor coupled to the memory and configured to store, into the storage device, a plurality of data blocks including a plurality of data patterns, classify the plurality of data blocks into the plurality of data patterns, for each of the plurality of data patterns, count numbers of the classified plurality of data blocks classified into each of the plurality of data patterns, read a first data block among the plurality of data blocks from the storage device, select a first data pattern from the plurality of data patterns based on the counted numbers when an error is detected in first data included in the first data block, replacing the first data included in the first data block with the selected first data pattern, and output the first data block including the first data pattern.