According to one embodiment, when a controller writes update data in a second memory to a first memory which is nonvolatile and a difference between a size of a page and a size of the update data is equal to or greater than a size of a cluster, the controller configured to generate write data by adding, to the update data, data which has the size of the cluster, store an update content of management information corresponding to the update data and an update content storage position indicating a storage position of the update content of the management information in the first memory, and write the generated write data to a block in writing of the first memory.