Data storage device and operating method to perform wear leveling based on elapsed time and write count

1. A data storage device comprising:

a nonvolatile memory device including a memory region, the memory region including a plurality of memory units; and

a controller suitable for monitoring an elapsed time and a write count of the memory region, and performing a wear leveling operation for at least one memory unit selected among the plurality of memory units depending on a monitoring result,

wherein the controller performs the wear leveling operation by comparing the elapsed time with a critical time which is set based on a drift time of the memory region, and

wherein the drift time is time required for a resistance value of a memory cell existing in a set state to increase to a resistance value of a memory cell in a reset state from the time when a write operation is performed on the memory cell.

2. The data storage device according to claim 1 , wherein the controller performs the wear leveling operation when the elapsed time reaches the critical time or when the write count reaches a critical count.

3. The data storage device according to claim 1 , wherein the controller resets the elapsed time and the write count after performing the wear leveling operation, and begins to measure again an elapsed time and a write count.

4. The data storage device according to claim 1 , wherein the controller performs the wear leveling operation by exchanging and storing data stored in a first memory unit and data stored in a second memory unit, which are selected sequentially among the plurality of memory units.

5. The data storage device according to claim 1 , wherein the controller performs the wear leveling operation by storing data stored in a memory unit selected sequentially among the plurality of memory units, in a memory unit previously designated as a gap, and designating the selected memory unit as a new gap.

6. The data storage device according to claim 1 , wherein the critical time is a time that is obtained through dividing the drift time by the number of the memory units.

7. A method for operating a data storage device, comprising:

monitoring an elapsed time and a write count of a memory region including a plurality of memory units; and

performing a wear leveling operation for at least one memory unit selected among the plurality of memory units by comparing the elapsed time with a critical time which is set based on a drift time of the memory region,

wherein the drift time is time required for a resistance value of a memory cell existing in a set state to increase to a resistance value of a memory cell in a reset state from the time when a write operation is performed on the memory cell.

8. The method according to claim 7 , wherein the performing of the wear leveling operation comprises:

performing the wear leveling operation when the elapsed time reaches the critical time or when the write count reaches a critical count.

9. The method according to claim 7 , further comprising:

resetting the elapsed time and the write count after performing the wear leveling operation, and beginning to measure again an elapsed time and a write count.

10. The method according to claim 7 , wherein the performing of the wear leveling operation comprises:

exchanging and storing data stored in a first memory unit and data stored in a second memory unit, which are selected sequentially among the plurality of memory units.

11. The method according to claim 7 , wherein the performing of the wear leveling operation comprises:

storing data stored in a memory unit selected sequentially among the plurality of memory units, in a memory unit previously designated as a gap; and

designating the selected memory unit as a new gap.

12. The method according to claim 7 , wherein the critical time is a time that is obtained through dividing the drift time by the number of the memory units.

13. A data storage device comprising:

a nonvolatile memory device including a memory region which includes a plurality of memory units; and

a controller suitable for performing a wear leveling operation for the memory region with a cycle of a critical write count,

wherein the controller performs the wear leveling operation at latest within a critical time,

wherein the critical time is set based on a drift time of the memory region, and

wherein the drift time is time required for a resistance value of a memory cell existing in a set state to increase to a resistance value of a memory cell in a reset state from the time when a write operation is performed on the memory cell.

14. The data storage device according to claim 13 , wherein the critical time is a time that is obtained through dividing the drift time by the number of the plurality of memory units.

15. The data storage device according to claim 13 , wherein the controller performs the wear leveling operation by exchanging and storing data stored in a first memoryunit and data stored in a second memory unit, which are selected sequentially among the plurality of memory units.

16. The data storage device according to claim 13 , wherein the controller performs the wear leveling operation by storing data stored in a memory unit selected sequentially among the memory units, in a memory unit previously designated as a gap, and designating the selected memory unit as a new gap.