Patent ID: 7434097

Claim:
An apparatus for improving fault tolerance of a storage system, the apparatus comprising: a. a first set of disk drives; b. a second set of disk drives, the second set of disk drives in power-off condition; c. a processing unit, the processing unit comprising: i. a drive replacement logic unit, the drive replacement logic unit identifying a potential failing disk drive from the first set of disk drives that has not failed yet; ii. a drive control unit, the drive control unit receiving an indication from the drive replacement logic unit to replace the potential failing disk drive with a spare disk drive from the second set of disk drives, the drive control unit powering-on the spare disk drive before the potential failing disk drive fails to replace the potential failing disk drive; and d. a data copying mechanism to copy data to the powered-on spare disk drive, the data being a copy of data stored on the potential failing disk, wherein data copying mechanism stores data received by the storage system to the potential failing disk drive and to the spare disk drive.