According to an embodiment, a memory system includes memory chips operable in parallel and a memory controller. The memory chips each include first storage areas. The memory controller generates first groups each including first storage areas selected from different memory chips. The memory controller generates second groups each being constituted by a minimum number of first storage areas composed by excluding one or more first storage areas from each of the first groups. The minimum number of first storage areas are capable of storing at least a first amount of data received from the host. The memory controller executes writing of the data to all the minimum number of first storage areas constituting one second group.