According to one embodiment, a nonvolatile memory includes a memory chip and a command processing unit. The command processing unit stores data read from a first position of the memory chip in a memory when a first command for compaction is received from a controller, transmits validity determination information used for determining whether or not the data read from the first position is valid to the controller, and writes valid data of the data stored in the memory to a second position of the memory chip when a second command for the compaction and validity identification information that identifies the valid data are received from the controller.