Patent ID: 7565439

Claim:
A storage system which is connected to a host computer, which comprises a storage unit for storing data and communicates using a TCP protocol having a delayed acknowledgement response (Delayed ACK) to provide a deliberate delay of transmission of an acknowledgement of a received packet, comprising: an operation mode determination unit which determines a data processing operation mode for said storage system; and a data processing unit which performs predetermined data processing according to said operation mode, wherein said operation mode determination unit determines whether or not to transmit a precedence packet that informs the host computer not to send a Delayed ACK before returning data which has been requested from said host computer, based on the length A of the data requested from said host computer, on the length B of data which can be transmitted to said host computer, and a value C obtained by dividing A by B, and being rounded up to the next integer; wherein, if C is not a multiple of a delayed packet number of a Delayed ACK, said data processing unit transmits said precedence packet before returning said data requested from said host computer, and thereafter transmits said data to the host computer after said precedence packet is transmitted to said host computer, and wherein said precedence packet is information which can be recognized by the protocol which is used by said host computer in transmission with said storage system, and is information which does not require an acknowledgement to be transmitted for verifying that said precedence packet has been received by said host computer.