A data storage system includes three or more storage devices, each associated with a unique data volume. A first one of the data storage devices at least has two or more data storage areas but can have more storage areas, which can be either data storage areas or parity storage areas. A second data storage device at least has two storage areas, one of which is a data storage area. A third data storage device at least has a parity storage area but can have more storage areas, which can be either data storage areas or parity storage areas. A first group of corresponding storage areas is defined by at least the data storage areas of the first and second storage devices and the parity storage area of the third storage device. A second group of corresponding storage areas is defined by at least the storage areas of the first and second storage devices. When a data segment is written to one of the data storage areas of a storage device, parity information can be updated using information read from one or more storage areas of the group of corresponding storage areas having the data storage area to which the data segment is written.