To provide a disk management method and a RAID storage system.

In a RAID storage system 16, physical disks 11a-11d are connected and a RAID group is comprised of the same stripe lines of the plurality of physical disks 11a-11d. The RAID group comprised of the stripe lines of the physical disks 11a-11d comprises therein the plurality of physical disks 11a-11d setting temporary closing areas 15a-15l by the unit of a plurality of virtual logic blocks of smaller units, a temporary closing mode management table 8 for managing the temporary closing areas of the physical disks, and a timer 7 for monitoring the lapse of a monitoring time from the reception of instruction from a higher order device to a response. When the monitoring time from the instruction reception to the response on the basis of the timer 7 exceeds a predetermined management time, a temporary closing area wherein a fault occurs, is temporarily closed.