Patent ID: 8009501

Claim:
A storage apparatus connected to a host system for sending and receiving data to and from said host system, comprising: a first data storage unit of a plurality of data storage units for storing write data requested by said host system; an access history storage unit for storing, when there is a write request for writing data into said first data storage unit or a read request for reading data stored in said first data storage unit, history of said write request or read request as access history; an operational information storage unit for storing operational information showing whether said first data storage unit is operating; an access prediction unit for predicting whether said first data storage unit will be accessed based on said access history; a send processing unit for delaying an error message for a given length of time when said first data storage unit is shut off and there is a read request for reading data stored in said first data storage unit; and an operational control unit for performing operational control of pre-starting said first data storage unit when said first data storage unit is shut off and said access prediction unit predicts that said first data storage unit will be accessed, or stopping said first data storage unit when said first data storage unit is operating and said access prediction unit predicts that said first data storage unit will not be accessed.