A RAID system having {HEAD ~ a plurality} of {TAIL ~ disk devices} and a RAID control device for controlling the plurality of disk devices, and storing same data in the plurality of disk devices, the system comprising: 
A RAID system having { HEAD ~ a plurality } of { TAIL ~ disk devices } and a RAID control device for controlling the plurality of disk devices , and storing same data in the plurality of disk devices , the system comprising :
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH