A storage system is known in which a plurality of flash memory packages (hereinafter referred to as “FM packages”) form a parity group in order to enhance redundancy of data. The FM package is a storage device equipped with a plurality of flash memory chips (hereinafter referred to as “FM chips”). PTL 1 describes a storage system that allows the FM package to execute a parity generation process when data related to a write request received from a host is stored in the FM package.