Storage device and operating method of storage device

A storage device, comprising:

• a nonvolatile memory device including a plurality of memory cells;
• and
• a memory controller configured to transmit a first read command and first read voltage information associated with the plurality of memory cells to the nonvolatile memory device, to receive first data from the nonvolatile memory device based on the first read command, and to perform error correction on the first data,
• wherein, when the error correction fails, the memory controller is further configured to transmit a first offset, a second read command and second read voltage information associated with the plurality of memory cells to the nonvolatile memory device, to receive second data from the nonvolatile memory device based on the second read command, and to perform a first soft decision process based on the second data,
• wherein, when the first soft decision process fails, the memory controller is further configured to transmit a third read command and third read voltage information associated with the plurality of memory cells to the nonvolatile memory device, to receive third data from the nonvolatile memory device based on the third read command, to transmit a fourth read command and fourth read voltage information associated with the plurality of memory cells to the nonvolatile memory device, and to receive fourth data from the nonvolatile memory device based on the fourth read command, and
• wherein the memory controller is further configured to adjust the first offset to a second offset based on the third data and the fourth data, to transmit the second offset, a fifth read command and fifth read voltage information associated with the plurality of memory cells to the nonvolatile memory device, to receive fifth data from the nonvolatile memory device based on the fifth read command, and to perform a second soft decision process based on the fifth data.

An operating method of a storage device which includes a nonvolatile memory device and a controller to control the nonvolatile memory device, the operating method comprising:

• reading, at the controller, first data and second data from the nonvolatile memory device by using a first read voltage and a second read voltage, respectively;
• adjusting, at the controller, an offset based on the first data and the second data;
• reading, at the controller, third data from the nonvolatile memory device by using a third read voltage and the adjusted offset;
• and
• performing, at the controller, a soft decision process based on the third data.