Storage unit, storage unit control method, and storage system

A method of controlling a storage unit connected communicably to a plurality of other storage units each having a plurality of first hard disk drives on which data is stored and having a plurality of second hard disk drives on which data is stored, said method comprising the steps of:

• receiving copies of first storage data and first identifiers from said other storage units, said first storage data being stored in a plurality of storage blocks created by logically partitioning a data storage area of said plurality of first hard disk drives, said first identifiers identifying the storage blocks;
• calculating an exclusive OR of the copies of the first storage data, with a correspondence established among the first identifiers, from the copies of the first storage data received from said other storage units;
• and
• storing a calculation result of the exclusive OR into storage blocks of said second hard disk drives, said storage blocks of said second hard disk drives having second identifiers corresponding to the first identifiers, said second identifiers individually identifying a plurality of storage blocks created by logically partitioning a data storage area of said plurality of second hard disk drives.

A storage system comprising a plurality of first storage units each having a plurality of first hard disk drives on which data is stored;

• and a second storage unit connected communicably to the first storage units and having a plurality of second hard disk drives on which data is stored,
• wherein said first storage unit comprises:
• a first data sending unit that sends a copy of first storage data and first identifiers to said second storage unit, said first storage data being stored in a plurality of storage blocks created by logically partitioning a data storage area of said plurality of first hard disk drives, said first identifiers identifying the storage blocks,
• said second storage unit comprises:
• a first data receiving unit that receives copies of the first storage data and the first identifiers from said first storage units;
• a first data operation controller that calculates an exclusive OR of the copies of the first storage data, with a correspondence established among the first identifiers, from the copies of the first storage data received by said first receiving unit from said first storage units;
• and
• a first data storage controller that stores a calculation result of the exclusive OR, calculated by said first data operation controller, into storage blocks of said second hard disk drives, said storage blocks of said second hard disk drives having second identifiers corresponding to the first identifiers, said second identifiers individually identifying a plurality of storage blocks created by logically partitioning a data storage area of said plurality of second hard disk drives.