A storage device includes first and second memory devices, and a memory controller. The first memory devices correspond to a main data area. The second memory devices correspond to a reserved area. The memory controller is coupled to the first and second memory devices through first and second channels. A number of first memory devices coupled to the memory controller through the first channel is equal to a number of first memory devices coupled to the memory controller through the second channel, and a number of second memory devices coupled to the memory controller through the first channel is different from a number of second memory devices coupled to the memory controller through the second channel. The memory controller selects a memory device on which a write operation is to be performed, based on a memory state of the first and second memory devices.