Memory system managing number of read operations using two counters

A memory system comprising:

• a nonvolatile memory including a memory cell array that includes a plurality of first units and at least one second unit, the second unit including the plurality of first units, the plurality of first units including at least a third unit;
• and
• a controller configured to:
• manage a plurality of first counts, each of the plurality of first counts indicating the number of read operations performed on one of the plurality of first units, and
• in response to a read operation being executed on the third unit and the first count for the third unit reaching a first threshold value, update a second count for the second unit, and
• in response to a total value of the first count for the third unit and the second count reaching a second threshold value, determine whether to rewrite data stored in at least one of the plurality of first units included in the second unit.

A method of controlling a nonvolatile memory that includes a memory cell array including a plurality of first units and at least one second unit, the second unit including the plurality of first units, the plurality of first units including at least a third unit, the method comprising:

• managing a plurality of first counts, each of the plurality of first counts indicating the number of read operations performed on one of the plurality of first units;
• in response to a read operation being executed on the third unit and the first count for the third unit reaching a first threshold value, updating a second count for the second unit;
• and
• in response to the second count reaching a second threshold value, determining whether to rewrite data stored in at least one of the plurality of first units included in the second unit.