According to one embodiment, a memory system includes a nonvolatile semiconductor memory include a first area, and a second area smaller than the first area; and a controller configured to control data stored in the nonvolatile semiconductor memory, wherein the nonvolatile semiconductor memory is configured to store a first data accessible by a host command and to a second data inaccessible by the host command, and when receiving the host command, the controller writes the second data of the first area within the second area and initializes a first address information related the first data.