Disk array apparatus and backup method of data

A backup method in a disk array apparatus, comprising:

• providing a disk array apparatus which comprises:
• first and second RAID (Redundant Arrays of Inexpensive Disks) groups;
• and
• a disk array controller,
• wherein said first RAID groups comprises a first data disk group of a first disk group and a second disk group which store first and second data, respectively;
• and a first redundant disk configured to store a first redundant data for said first and second data;
• wherein said second RAID groups comprises a second data disk group of a third disk group and a fourth disk group which store second data, respectively;
• and a second redundant disk configured to store second redundant data for said third and fourth data, each of said first to fourth disk group including at least one disk;
• reconfiguring said first to fourth disk groups other than a first specific disk and said first and second redundant disks into a third RAID group when said first specific disk which stores a first specific data is failed in said fourth disk group;
• issuing a first redundant data generation instruction when said first specific disk is failed in said fourth disk group in response to the first redundant data generation instruction;
• generating a third redundant data based on said first to third data, said fourth data other than a data corresponding to said first specific disk, and said second redundant data;
• and
• writing said third redundant data into said first redundant disk.