Storage control device and method for controlling storages

1. A storage control device comprising:

a memory; and

a processor to

copy all pieces of first information stored in a first storage to a backup volume,

store management information in the memory when a first piece of the first information stored in the first storage is updated to second information after the copy, the management information including position information indicating a stored position, in the first storage, of the first piece of the first information, the first storage being included in a storage group in which redundancy is maintained, the storage group including a plurality of storages,

execute, when a first failure occurs in the first storage, first restoration on the basis of the management information stored in the memory and reference information stored in reference storages, the reference storages being the plurality of storages other than the first storage, the first restoration restoring the second information stored at the stored position in the first storage to a spare storage other than the plurality of storages,

execute second restoration on the basis of the management information stored in the memory and the reference information stored in the reference storages, the second restoration restoring third information to the spare storage, the third information being stored in the first storage and being other than the second information,

stop the second restoration when a second failure occurs in a second storage among the reference storages while the second restoration is being executed, and

execute third restoration on the basis of the first information stored in the backup volume and the management information stored in the memory, the third restoration restoring fourth information to the spare storage, the fourth information being stored in the first storage and being other than the second information.

2. The storage control device according to claim 1 , wherein

the processor executes the third restoration on the basis of progress information indicating progress of the second restoration, and

the fourth information is other than the third information.

3. The storage control device according to claim 1 , wherein

the processor

receives a write request while one of the first restoration and the second restoration is being executed, and

writes data specified in the write request to the spare storage and the reference storages, in a storage region designated by the write request.

4. The storage control device according to claim 1 , wherein

the processor

receives a read request while one of the first restoration, the second restoration, and the third restoration is being executed,

determines whether read target information stored in a storage region designated by the read request is restored information that has been restored by one of the first restoration, the second restoration, and the third restoration, and

executes, on the basis of a result of the determination, one of first read processing and second read processing, the first read processing reading the read target information from the spare storage and the reference storages, the second read processing reading the read target information from the backup volume.

5. The storage control device according to claim 4 , wherein

the processor executes, upon receiving the read request while the third restoration is being executed, the first read processing when it is determined that the read target information is the restored information, and

the processor executes, upon receiving the read request while the third restoration is being executed, the second read processing when it is determined that the read target information is not the restored information.

6. The storage control device according to claim 4 , wherein

upon receiving the read request while the first restoration is being executed, the processor determines on the basis of the management information stored in the memory and progress information indicating progress of the first restoration, whether the read target information is first restored information that has been restored by the first restoration,

the processor executes the first read processing when it is determined that the read target information is the first restored information, and

the processor obtains, when it is determined that the read target information is not the first restored information, information identical with the read target information on the basis of the reference information stored in the reference storages.

7. The storage control device according to claim 4 , wherein

the processor determines, upon receiving the read request while the first restoration is being executed, whether three conditions including a first condition, a second condition, and a third condition are satisfied,

the first condition is that progress information indicating progress of the first restoration indicates that the first restoration has not reached the storage region,

the second condition is that the storage region is not indicated by the management information before the first restoration is started,

the third condition is that the storage region is indicated by the management information after the first restoration is started, and

the processor executes the first read processing when it is determined that the three conditions are satisfied.

8. The storage control device according to claim 1 , further comprising:

a computer including the processor.

9. A method for controlling storages, the method comprising:

copying, by storage control device, all pieces of first information stored in a first storage to a backup volume;

storing management information in a memory when a first piece of the first information stored in the first storage is updated to second information after the copying, the management information including position information indicating a stored position, in the first storage, of the first piece of the first information, the first storage being included in a storage group in which redundancy is maintained, the storage group including a plurality of storages;

executing, when a first failure occurs in the first storage, first restoration on the basis of the management information stored in the memory and reference information stored in reference storages, the reference storages being the plurality of storages other than the first storage, the first restoration restoring the second information stored at the stored position in the first storage to a spare storage other than the plurality of storages;

executing second restoration on the basis of the management information stored in the memory and the reference information stored in the reference storages, the second restoration restoring third information to the spare storage, the third information being stored in the first storage and being other than the second information;

stopping the second restoration when a second failure occurs in a second storage among the reference storages while the second restoration is being executed; and

executing third restoration on the basis of the first information stored in the backup volume and the management information stored in the memory, the third restoration restoring fourth information to the spare storage, the fourth information being stored in the first storage and being other than the second information.

10. A computer-readable recording medium storing a program that causes a computer to execute a procedure, the procedure comprising:

copying all pieces of first information stored in a first storage to a backup volume;

storing management information in a memory when a first piece of the first information stored in the first storage is updated to second information after the copying, the management information including position information indicating a stored position, in the first storage, of the first piece of the first information, the first storage being included in a storage group in which redundancy is maintained, the storage group including a plurality of storages;

executing, when a first failure occurs in the first storage, first restoration on the basis of the management information stored in the memory and reference information stored in reference storages, the reference storages being the plurality of storages other than the first storage, the first restoration restoring the second information stored at the stored position in the first storage to a spare storage other than the plurality of storages;

executing second restoration on the basis of the management information stored in the memory and the reference information stored in the reference storages, the second restoration restoring third information to the spare storage, the third information being stored in the first storage and being other than the second information;

stopping the second restoration when a second failure occurs in a second storage among the reference storages while the second restoration is being executed; and

executing third restoration on the basis of the first information stored in the backup volume and the management information stored in the memory, the third restoration restoring fourth information to the spare storage, the fourth information being stored in the first storage and being other than the second information.