A data storage method includes that a first device generates N check units for M data units, where M and N are both positive integers, and M+N=K. The first device stores the K units in K hard disk modules in the storage system, where the K units include the M data units and the N check units. Each of the K hard disk modules stores one of the K units. Each hard disk module includes an interface module and a hard disk, and the interface module communicates with the hard disk.