An object storage system includes a plurality of memory devices; and a memory controller configured to, receive a value and a key from a host, the key identifying the received value, store data corresponding to the received value in the plurality of memory devices, generate, based on the received value, a parity for detecting an error of the stored data, manage key-value mapping information that identifies a correspondence relationship between the received value and the key, and manage the parity in the key-value mapping information such that the parity corresponds to the received value and the key.