Memory system and data relocating method

A memory system comprising:

• a nonvolatile semiconductor memory that includes a plurality of blocks;
• and
• a memory controller circuit configured to:
• select a first block and a second block from the plurality of blocks, the first block being a garbage collection target block, the second block being a wear leveling target block or a refresh target block,
• relocate first data which is valid data stored in the first block in a series of write operations to a third block including a first write operation and a second write operation, the third block being a block having a free region among the plurality of blocks, and
• relocate second data which is valid data stored in the second block in a series of write operations to a fourth block including a third write operation, the fourth block having a free region and being a different block from the third block among the plurality of blocks, wherein the third write operation is performed between the first operation and the second write operation.