A computer system comprising computers, each the computers is coupled to a storage apparatus storing at least one file including records, each the computers includes a file system, a key-value data management module, and a loader, each the computers holds key-value data structure information, the loader being configured to identify a file to be processed in which the at least one piece of the updated key-value data is to be reflected; and transmit a request to update the file including the at least one piece of the updated key-value data; and the file system being configured to identify the position of one of the records corresponding to the piece of updated key-value data within the file based on the key-value data structure information, and update the file by writing the at least one piece of the updated key-value data.