Patent ID: 7904749

Claim:
A storage system comprising: a first storage device having a first plurality of hard disk drives and a first controller controlling said first plurality of hard disk drives; wherein said first controller stores data in said first plurality of hard disk drives by stripes, each stripe includes M data and N parity data, where M and N are integers, and said first controller calculates for each stripe said N parity data using said M data, wherein said M data and N parity data of said each stripe are allocated to M+N hard disk drives of said first plurality of hard disk drives, wherein a first hard disk drive of said first plurality of hard disk drives includes data or parity data of both a first stripe of said stripes and a second stripe of said stripes, while a second hard disk drive of said first plurality of hard disk drives includes data or parity data of only one of said first stripe of said stripes or said second stripe of said stripes, wherein during data recovery involving failure of one of the first plurality of hard disk drives as a failed hard disk drive, the data in the failed hard disk drive is recovered for each stripe by calculation using data and parity data in other hard disk drives of the first plurality of hard disk drives for said each stripe.