A data management system and method for processing distributed data, which adaptively adjusts the amounts of data to be read from a plurality of storages, depending on I/O performances of the respective storages. The data management system includes a plurality of storage nodes each storing duplicate data of original data, and a distributed data management unit providing read requests for parts of the duplicate data to the respective storage nodes, combining the read parts into a complete version of the data, and outputting the complete version of the data.