Storage apparatus, storage system, and data management method

1. A storage apparatus comprising a control unit configured to manage data that is divided into a plurality of data elements and is stored in a plurality of storage devices, wherein

a plurality of old redundancy codes generated in advance by a plurality of different calculation methods for data containing a plurality of data elements are stored in the storage devices as redundancy codes for the data, and

the control unit includes:

a detecting unit that is configured to detect that the data is incorrect;

an identification unit that is configured to, when the detection unit detects that the data is incorrect, determine that a first data element contained in the data is incorrect, when a first restoration calculation first data element, which is restored from the first data element using other data elements of the data excluding the first data element and a new redundancy code obtained from the data by a first calculation method, coincides with a second restoration calculation first data element, which is restored from the first data element using the other data elements and a new redundancy code obtained from the data by a second calculation method; and

a restoration unit that is configured to correct the first data element in the storage devices that is determined to be incorrect by the identification unit, to either the first restoration calculation first data element or the second restoration calculation first data element.

2. The storage apparatus according to claim 1 , wherein

the control unit further includes:

a detection unit that is configured to calculate new redundancy codes from the data stored in the storage devices by the plurality of calculation methods, when old redundancy codes and new redundancy codes corresponding to the old redundancy codes coincide in all calculation methods, to determine that neither the data nor the old redundancy codes are incorrect, while when old redundancy codes and new redundancy codes corresponding to the old redundancy codes do not coincide in all calculation methods, to determine that the data is incorrect, and when old redundancy codes and new redundancy codes corresponding to the old redundancy codes do not coincide in part of the calculation methods, to determine that the old redundancy codes are incorrect, and wherein

the identification unit is configured to, when the data is determined to be incorrect by the detection unit, identify which data element contained in the data is incorrect.

3. The storage apparatus according to claim 2 , wherein

the detection unit is configured to, when determining that the old redundancy codes are incorrect, correct redundancy codes in the storage devices to the new redundancy codes.

4. The storage apparatus according to claim 1 , wherein

the identification unit is configured to search for incorrect data elements while changing the number of data elements to be excluded as the first data element in a range of from one to (the number of redundancy codes-1).

5. The storage apparatus according to claim 2 , wherein

the detection unit is configured to, when data movement occurs between storage devices, execute processing according to the data movement.

6. The storage apparatus according to claim 1 , wherein

either the identification unit or the restoration unit, or both thereof are achieved by the processor executing a program stored in a memory within the storage apparatus.

7. The storage apparatus according to claim 1 , wherein

either the identification unit or the restoration unit, or both thereof are configured of a hardware circuit in the storage apparatus.

8. A storage system comprising:

a storage apparatus in which data is divided into a plurality of data elements and is stored in a plurality of storage devices, and a plurality of old redundancy codes generated in advance by a plurality of different calculation methods for data containing a plurality of data elements are stored in the storage devices as redundancy codes for the data; and

an external apparatus that is coupled to the storage apparatus through a network, wherein

the external apparatus includes:

a detecting unit that is configured to detect that the data is incorrect;

an identification unit that is configured to, when the detection unit detects that the data is incorrect, determine that a first data element contained in the data is incorrect, when a first restoration calculation first data element, which is restored from the first data element using other data elements of the data excluding the first data element and a new redundancy code obtained from the data by a first calculation method, coincides with a second restoration calculation first data element, which is restored from the first data element using the other data elements and a new redundancy code obtained from the data by a second calculation method; and

a restoration unit that is configured to correct the first data element in the storage devices that is determined to be incorrect by the identification unit, to either the first restoration calculation first data element or the second restoration calculation first data element.

9. A data management method for a storage apparatus in which data is divided into a plurality of data elements and is stored in a plurality of storage devices,

a plurality of old redundancy codes generated in advance by a plurality of different calculation methods for data containing a plurality of data elements being stored in the storage devices as redundancy codes for the data,

the data management method comprising:

detecting that the data is incorrect;

determining that, when it is detected that the data is incorrect, a first data element contained in the data is incorrect, when a first restoration calculation first data element, which is restored from the first data element using other data elements of the data excluding the first data element and a new redundancy code obtained from the data by a first calculation method, coincides with a second restoration calculation first data element, which is restored from the first data element using the other data elements and a new redundancy code obtained from the data by a second calculation method; and

correcting the first data element in the storage devices that is determined to be incorrect, to either the first restoration calculation first data element or the second restoration calculation second data element.

10. The data management method according to claim 9 , comprising:

calculating new redundancy codes from the data stored in the storage devices by the plurality of calculation methods;

when old redundancy codes and new redundancy codes corresponding to the old redundancy codes coincide in all calculation methods, determining that neither the data nor the old redundancy codes are incorrect;

when old redundancy codes and new redundancy codes corresponding to the old redundancy codes do not coincide in all calculation methods, determining that the data is incorrect;

when old redundancy codes and new redundancy codes corresponding to the old redundancy codes do not coincide in part of the calculation methods, determining that the old redundancy codes are incorrect; and

when the data is determined to be incorrect, identifying which data element contained in the data is incorrect.