a nonvolatile memory device including a first memory region having a first write speed and a second memory region having a second write speed different from the first write speed; and

a storage controller including an internal buffer, the storage controller configured to store data from an external host in the first memory region by priority in a first mode,

wherein the storage controller is configured to control a data migration operation by:

performing read operation-transfer operation to read a second data that is pre-stored in the first memory region by a first unit and to transfer the first unit of data to a data input/output (I/O) circuit of the nonvolatile memory device a plurality of times; and

storing the second data transferred to the data I/O circuit in the second memory region.