Question: Many RAID implementations allow on-line repair in which the system continues to operate after a disk failure, while a new empty disk is inserted to replaced the failed disk, and while regenerating and copying data to the new disk. Sketch a design for a 2-disk, mirrored RAID that allows the system to remain on-line during reconstruction, while still ensuring that when the data copying is done, the new disk is properly reconstructed (i.e., it is an exact copy of other disk.) In particular, specify
(1) what is done by a recovery thread,
(2) what is done on a read during recovery, and
(3)
Also explain why your system will operate correctly even if a crash occurs in the middle of reconstruction.