Memory system and control method thereof

A memory system comprising:

• a non-volatile memory having a plurality of memory cells;
• and
• a controller configured to control writing, reading, and erasing of data to and from the non-volatile memory,
• wherein the non-volatile memory includes
• a page for which the data is written into and read from at least a part of the plurality of memory cells, and
• a block having a plurality of the pages,
• the controller is configured to
• manage a first block group including a plurality of the blocks and a second block group including a plurality of the first block groups, and
• generate a first parity and a second parity, the first parity being a parity for correcting an error occurring in the second block group by data in each of the plurality of first block groups in the second block group, and the second parity being a parity for correcting an error occurring in the first block group by data in the first block group.