Storage system, storage control apparatus, and storage control method

1. A storage system comprising:

first storage devices constituting a first logical storage area;

second storage devices constituting a second logical storage area; and

a storage control apparatus configured to perform a procedure including:

controlling processing for accessing first data stored in the first logical storage area and second data stored in the second logical storage area,

managing the first logical storage area and the second logical storage area in such a manner that the first data stored in the first logical storage area and the second data stored in the second logical storage area have redundancy, and first parity data for the first data are stored in first parity storage areas which are distributedly arranged in more than one of the first storage devices, and second parity data for the second data are stored in second parity storage areas which are distributedly arranged in more than one of the second storage devices, and

when failure occurs in one or more of the first storage devices constituting part of the first logical storage area, generating part of the first data which are stored, before the failure, in the one or more of the first storage devices, and writing the part of the first data over part of the second parity data stored in at least part of the second parity storage areas in the second logical storage area.

2. The storage system according to claim 1 , wherein the procedure further includes, after the one or more of the first storage devices are replaced with one or more replacements, transferring the part of the first data stored in the at least part of the second parity storage areas to the one or more replacements of the one or more of the first storage devices, calculating at least part of the second parity data which are stored in the at least part of the second parity storage areas before the storing of the part of the first data, on a basis of part of the second data stored in the second logical storage area other than the at least part of the second parity storage areas, and writing the at least part of the second parity data in the at least part of the second parity storage areas.

3. The storage system according to claim 1 , wherein the procedure further includes selecting as the second logical storage area a designated logical storage area to which a priority equal to or lower than a priority assigned to the first logical storage area is assigned, when the failure occurs in the one or more of the first storage devices and the second logical storage area stores the second data with triple redundancy.

4. The storage system according to claim 1 , wherein the procedure further includes selecting as the second logical storage area a designated logical storage area to which a priority lower than a priority assigned to the first logical storage area is assigned, when the failure occurs in the one or more of the first storage devices and the second logical storage area stores the second data with double redundancy.

5. The storage system according to claim 1 , wherein the procedure further includes, after the failure occurs in the one or more of the first storage devices and the part of the first data is stored in the at least part of the second parity storage areas, incorporating into the first logical storage area the at least part of the second parity storage areas as one or more refuges from the one or more of the first storage devices, resuming managing of the first logical storage area while maintaining redundancy in the first data, separating the at least part of the second parity storage areas from the second logical storage area, and resuming managing of the second logical storage area with lowered redundancy in the second data.

6. The storage system according to claim 5 , wherein the procedure further includes determining, according to a history of requests for access to the second logical storage area received from a host apparatus during a predetermined past period, whether to read out requested data from the at least part of the second parity storage areas, or to calculate the requested data a basis of data stored in the first storage devices other than the one or more of the first storage devices, when the requested data is stored, before the failure, in the one or more of the first storage devices and is requested to be read out by the host apparatus under a condition that the at least part of the second parity storage areas is incorporated into the first logical storage area.

7. The storage system according to claim 5 , wherein the procedure further includes determining, according to a number of unexecuted requests for access to the second logical storage area received from a host apparatus, whether to read out requested data from the at least part of the second parity storage areas, or to calculate the requested data on a basis of data stored in the first storage devices other than the one or more of the first storage devices, when the requested data is stored, before the failure, in the one or more of the first storage devices and is requested to be read out by the host apparatus under a condition that the at least part of the second parity storage areas is incorporated into the first logical storage area.

8. A storage control method comprising:

controlling processing for accessing first data stored in a first logical storage area and second data stored in a second logical storage area, where the first logical storage area is constituted by first storage devices and the second logical storage area is constituted by second storage devices;

managing the first logical storage area and the second logical storage area in such a manner that the first data stored in the first logical storage area and the second data stored in the second logical storage area have redundancy, and first parity data for the first data are stored in first parity storage areas which are distributedly arranged in more than one of the first storage devices, and second parity data for the second data are stored in second parity storage areas which are distributedly arranged in more than one of the second storage devices; and

when failure occurs in one or more of the first storage devices constituting part of the first logical storage area, generating part of the first data which are stored, before the failure, in the one or more of the first storage devices, and writing the part of the first data over part of the second parity data in at least part of the second parity storage areas in the second logical storage area.

9. The storage control method according to claim 8 , further comprising:

after the one or more of the first storage devices are replaced with one or more replacements, transferring the part of the first data stored in the at least part of the second parity storage areas to the one or more replacements of the one or more of the first storage devices, calculating at least part of the second parity data which are stored in the at least part of the second parity storage areas before the storing of the part of the first data, on a basis of part of the second data stored in the second logical storage area other than the at least part of the second parity storage areas, and writing the at least part of the second parity data in the at least part of the second parity storage areas.

10. The storage control method according to claim 8 , further comprising:

selecting as the second logical storage area a designated logical storage area to which a priority equal to or lower than a priority assigned to the first logical storage area is assigned, when the failure occurs in the one or more of the first storage devices and the second logical storage area stores the second data with triple redundancy.

11. The storage control method according to claim 8 , further comprising:

selecting as the second logical storage area a designated logical storage area to which a priority lower than a priority assigned to the first logical storage area is assigned, when the failure occurs in the one or more of the first storage devices and the second logical storage area stores the second data with double redundancy.

12. The storage control method according to claim 8 , further comprising:

after the failure occurs in the one or more of the first storage devices and the part of the first data is stored in the at least part of the second parity storage areas, incorporating into the first logical storage area the at least part of the second parity storage areas as one or more refuges from the one or more of the first storage devices, resuming managing of the first logical storage area while maintaining redundancy in the first data, separating the at least part of the second parity storage areas from the second logical storage area, and resuming managing of the second logical storage area with lowered redundancy in the second data.

13. The storage control apparatus according to claim 12 , further comprising:

determining, according to a history of requests for access to the second logical storage area received from a host apparatus during a predetermined past period, whether to read out requested data from the at least part of the second parity storage areas, or to calculate the requested data on a basis of data stored in the first storage devices other than the one or more of the first storage devices, when the requested data is stored, before the failure, in the one or more of the first storage devices and is requested to be read out by the host apparatus under a condition that the at least part of the second parity storage areas is incorporated into the first logical storage area.

14. The storage control method according to claim 12 , further comprising:

determining, according to a number of unexecuted requests for access to the second logical storage area received from a host apparatus, whether to read out requested data from the at least part of the second parity storage areas, or to calculate the requested data on a basis of data stored in the first storage devices other than the one or more of the first storage devices, when the requested data is stored, before the failure, in the one or more of the first storage devices and is requested to be read out by the host apparatus under a condition that the at least part of the second parity storage areas is incorporated into the first logical storage area.

15. A storage control apparatus comprising a processor configured to perform a procedure including:

controlling processing for accessing first data stored in a first logical storage area and second data stored in a second logical storage area, where the first logical storage area is constituted by first storage devices and the second logical storage area is constituted by second storage devices;

managing the first logical storage area and the second logical storage area in such a manner that the first data stored in the first logical storage area and the second data stored in the second logical storage area have redundancy, and first parity data for the first data are stored in first parity storage areas which are distributedly arranged in more than one of the first storage devices, and second parity data for the second data are stored in second parity storage areas which are distributedly arranged in more than one of the second storage devices; and

when failure occurs in one or more of the first storage devices constituting part of the first logical storage area, generating part of the first data which are stored, before the failure, in the one or more of the first storage devices, and writing the part of the first data over part of the second parity data in at least part of the second parity storage areas in the second logical storage area.

16. The storage control apparatus according to claim 15 , wherein the procedure further includes, after the one or more of the first storage devices are replaced with one or more replacements, transferring the part of the first data stored in the at least part of the second parity storage areas to the one or more replacements of the one or more of the first storage devices, calculating at least part of the second parity data which are stored in the at least part of the second parity storage areas before the storing of the part of the first data, on a basis of part of the second data stored in the second logical storage area other than the at least part of the second parity storage areas, and writing the at least part of the second parity data in the at least part of the second parity storage areas.

17. The storage control apparatus according to claim 15 , wherein the procedure further includes, after the failure occurs in the one or more of the first storage devices and the part of the first data is stored in the at least part of the second parity storage areas, incorporating into the first logical storage area the at least part of the second parity storage areas as one or more refuges from the one or more of the first storage devices, resuming managing of the first logical storage area while maintaining redundancy in the first data, separating the at least part of the second parity storage areas from the second logical storage area, and resuming managing of the second logical storage area with lowered redundancy in the second data.

18. The storage control apparatus according to claim 17 , wherein the procedure further includes determining, according to a history of requests for access to the second logical storage area received from a host apparatus during a predetermined past period, whether to read out requested data from the at least part of the second parity storage areas, or to calculate the requested data on a basis of data stored in the first storage devices other than the one or more of the first storage devices, when the requested data is stored, before the failure, in the one or more of the first storage devices and is requested to be read out by the host apparatus under a condition that the at least part of the second parity storage areas is incorporated into the first logical storage area.

19. The storage control apparatus according to claim 17 , wherein the procedure further includes determining, according to a number of unexecuted requests for access to the second logical storage area received from a host apparatus, whether to read out requested data from the at least part of the second parity storage areas, or to calculate the requested data on a basis of data stored in the first storage devices other than the one or more of the first storage devices, when the requested data is stored, before the failure, in the one or more of the first storage devices and is requested to be read out by the host apparatus under a condition that the at least part of the second parity storage areas is incorporated into the first logical storage area.