Disk array having mirror configuration and rebuilding method therefor

A method for rebuilding a disk array having a mirror configuration comprising a buffer for temporarily storing data (data X) in a read or write request from a host (read/write request), a redundant first disk and second disk having a mirror configuration, an auxiliary disk used for rebuilding when the second disk fails, a redundancy management table for logging disk locations of data stored in the first disk and copied to the auxiliary disk, and a controller for controlling reading and writing of the data X between the buffer and two redundant disks in response to a read or write request, the method comprising:

• (a) copying, to the auxiliary disk, the data X stored in the buffer for rebuilding, in parallel with reading and writing the data X, when the second disk fails;
• (b) logging, in a redundancy management table, copied disk locations of the data X copied in (a);
• and
• (c) returning a ‘read/write request complete’ response to the host after completing the copying in (a), wherein the controller in (a), when a size of a current data X in the read/write request is smaller than a first predetermined value, in executing the rebuilding, reads data at a disk location contiguous with the data X stored in the buffer from a first disk, stores the data in the buffer, and copies the contiguous data stored in the buffer to the auxiliary disk as additional data such that an overall size of the data reaches a second predetermined value;
• and the controller in (b) logs the additional data in the redundancy management table.

A computer program product for rebuilding a disk array having a mirror configuration comprising a buffer for temporarily storing data (data X) in a read or write request from a host (read/write request), a redundant first disk and second disk having a mirror configuration, an auxiliary disk used for rebuilding when the second disk fails, a redundancy management table for logging disk locations of data stored in the first disk and copied to the auxiliary disk, and a controller for controlling reading and writing of the data X between the buffer and two redundant disks in response to a read or write request, the computer program product comprising a non-transitory storage medium comprising program code executable by the controller to perform:

• (a) copying, to the auxiliary disk, the data X stored in the buffer for rebuilding, in parallel with reading and writing the data X, when the second disk fails;
• (b) logging, in the redundancy management table, copied disk locations of the data X copied in (a);
• and
• (c) returning a ‘read/write request complete’ response to the host after completing the copying in (a), wherein the controller in (a), when a size of a current data X in the read/write request is smaller than a first predetermined value, in executing the rebuilding, reads data at a disk location contiguous with the data X stored in the buffer from a first disk, stores the data in the buffer, and copies the contiguous data stored in the buffer to the auxiliary disk as additional data such that an overall size of the data reaches a second predetermined value;
• and the controller in (b) logs the additional data in the redundancy management table.