FIGS. 5 and 6 are block diagrams illustrating an operating method of a storage device of FIG. 1. Referring to FIGS. 1, 4, and 5, the count management unit 121 of the controller 120 may count the number of read commands received from the host device and may manage a read count. For example, if the read count associated with the word lines WL1 and WL2 of the first zone Zone_1a of the selected memory block BLKz reaches a first threshold value N1, the count management unit 121 may perform the reliability verification read operation on each of the word lines WL1 and WL2. For example, the controller 120 may count the number of read commands associated with all the word lines WL1 and WL2 and may compare the count result with the first threshold value N1.

The controller 120 may read data “DATA” from memory cells of the first word line WL1. For example, the data read from memory cells of the first word line WL1 may include an error bit(s). The ECC circuit 122 may correct an error based on the result of detecting the number of error bits of the read data. If the number of error bits of the read data is smaller than the reference number of error bits, the ECC circuit 122 may correct the error of the read data.

The count management unit 121 may perform the reliability verification read operation on the second word line WL2 in a manner the same as or similar to that performed on the first word line WL1.