The count management unit 121 may count the number of times that a read command is received from the host device. According to an exemplary embodiment of the inventive concept, a count associated with the read command may be a “read count”.

In the case where a read count value reaches a threshold value, the count management unit 121 may perform a reliability verification read operation on a specific word line. For example, the count management unit 121 may perform the reliability verification read operation on the specific word line based on zone information received from the nonvolatile memory device 110. The reliability verification read operation will be more fully described with reference to FIGS. 5 to 7.

The FCC circuit 122 may detect and correct an error of data read from the nonvolatile memory device 110. For example, data stored in the nonvolatile memory device 110 may include an error due to various factors such as deterioration due to program and read operations, a temperature, and a time. The ECC circuit 122 may detect and correct an error included in data. The ECC circuit 122 may detect an error of data read from the nonvolatile memory device 110 through the reliability verification read operation. The reliability verification read operation may include operations of reading data from memory cells connected to any word line and measuring a bit error rate of the read data.