A memory system includes a nonvolatile memory having memory dies controlled in parallel and each including a plurality of physical blocks, and a controller. The controller manages a plurality of logical areas for storing data portions received from the host and parities calculated from the data portions, the logical areas including first and second logical areas for storing first and second parity groups, respectively. Each first parity group includes k data portions received from the host and m parities calculated therefrom. Each second parity group includes k′ data portions received from the host and m′ parities calculated therefrom. Also, the controller maps each logical area to storage locations in the non-volatile memory dies such that the data portions and the parities of any one parity group are each stored in a different physical block in a set of physical blocks selected from different non-volatile memory dies.