A storage system includes a controller and a nonvolatile memory drive, in which the controller transmits a write request that designates a volume identifier of a volume to be provided to a host, to the nonvolatile memory drive; the nonvolatile memory drive exclusively allocates a free block selected from a plurality of blocks to the volume identifier; write data of the write request is written to the free block; when the write data is update write data, an area that stores data to be updated is changed to an invalid data area; and after valid data of a block including the invalid data area is migrated to another block, all data of the block including the invalid data area is erased.