A storage system includes a storage device and an overlap checker. The overlap checker receives I/O commands of the storage device, extracts characteristics of the received I/O commands, issues a first merge command including N first I/O commands among the I/O commands in response to the extracted characteristics, wherein ‘N’ is a natural number greater than 1. And each of the first I/O commands instructs operation on a position corresponding to an offset in a region of the storage device corresponding to a logical address, wherein the characteristics of the I/O commands include the logical address and the offset.