Storage device and operating method thereof

A method for operating a storage device including a plurality of memory blocks, the method comprising:

• performing a read operation of reading data stored in the plurality of memory blocks based on a history read table including root bit information, read voltage information, and error bit information on each of the plurality of memory blocks;
• changing, when the read operation fails, a level of a read voltage and performing a read retry operation of retrying the read operation by using the changed read voltage;
• comparing, when the read retry operation passes, the root bit information of the read retry operation with the root bit information of the history read table;
• and
• determining whether the history read table is to be updated according to a result of the comparing.

An operating method of a controller, the operating method comprising:

• controlling a memory device to perform a read operation on a memory unit according to information on the memory unit, wherein the information includes root bit information, read voltage information and error bit count for the memory unit and the information is included in a history read table;
• controlling, when the read operation fails, the memory device to perform a read retry operation on the memory unit by changing a read voltage;
• and
• updating the history read table when the read retry operation has succeeded and when:
• the root bit information of the read retry operation is the same as the root bit information within the history read table, or
• the root bit information of the read retry operation is different from the root bit information within the history read table and the error bit count of the read retry operation is smaller than the error bit count within the history read table.