Method and device for storing data
A method is provided for storing data by distributing the data into plural storage units that are accessible independently of one another. The method includes the steps of dividing data to be stored into plural data blocks, generating parity data corresponding to the data blocks, distributing the plural data blocks and the parity data into the storage units to let the storage units store the same, responding to a situation where any of the storage units becomes inaccessible, reconstructing data stored in the storage unit that has become inaccessible before the situation occurs based on data stored in the remaining storage units, dividing the reconstructed data into plural reconstructed data blocks, generating parity data corresponding to the reconstructed data blocks, and distributing the plural reconstructed data blocks and the parity data corresponding thereto into accessible storage units to let the accessible storage units store the same.
1. A method for storing data with a controller by distributing the data into plural storage units that are accessible independently of one another; the method comprising:
dividing data to be stored into plural data blocks;
generating first parity data corresponding to the plural data blocks;
distributing the plural data blocks and the first parity data into the plural storage units to let the storage units store the plural data blocks and the first parity data;
responding to a situation where any of the plural storage units becomes inaccessible, reconstructing data stored in the storage unit that has become inaccessible before the situation occurs based on data stored in the remaining storage units;
dividing the data thus reconstructed into plural reconstructed data blocks;
generating second parity data corresponding to the plural reconstructed data blocks; and
distributing the plural reconstructed data blocks and the second parity data corresponding to the plural reconstructed data blocks into plural accessible storage units of the plural storage units to let the accessible storage units store the plural reconstructed data blocks and the second parity data.
2. The method according to claim 1 , further comprising, every time when one storage unit becomes inaccessible, reconstructing and dividing data stored in the storage unit that has become inaccessible to let the accessible storage units store reconstructed data blocks and parity data until the number of accessible storage units reaches one.
3. A data storage device comprising:
plural storage units that are accessible independently of one another; and
a controller for letting the plural storage units store data,
the controller including
a portion for dividing data to be stored into plural data blocks;
a portion for generating first parity data corresponding to the plural data blocks;
a portion for distributing the plural data blocks and the first parity data into the plural storage units to let the storage units store the plural data blocks and the first parity data;
responding to a situation where any of the plural storage units becomes inaccessible, a portion for reconstructing data stored in the storage unit that has become inaccessible before the situation occurs based on data stored in the remaining storage units;
a portion for dividing the data thus reconstructed into plural reconstructed data blocks;
a portion for generating second parity data corresponding to the plural reconstructed data blocks; and
a portion for distributing the plural reconstructed data blocks and the second parity data corresponding to the plural reconstructed data blocks into accessible storage units of the plural storage units to let the accessible storage units store the plural reconstructed data blocks and the second parity data.
4. The data storage device according to claim 3 , wherein each of the plural storage units is a closed structure that houses a storage medium therein.
5. The data storage device according to claim 4 , wherein the plural storage units include one or more magnetic hard disk drives as a storage medium.
6. The data storage device according to claim 3 , further comprising a portion for notifying when the number of accessible storage units is reduced to a predetermined number.