The invention further includes a control unit, when there is no access from the host unit to the logical unit for a predetermined time, for determining the disk units corresponding to {HEAD ~ the logical unit} based on {TAIL ~ information} recorded in the management information recording device and performing power saving of power supply for the disk units 
The invention further includes a control unit , when there is no access from the host unit to the logical unit for a predetermined time , for determining the disk units corresponding to { HEAD ~ the logical unit } based on { TAIL ~ information } recorded in the management information recording device and performing power saving of power supply for the disk units
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