PURPOSE: To shorten the processing time by controlling whether the processing is executed by the electronic disk processor receiving an input/output request or the other electronic disk processor in accordance with a load state of the electronic disk processor which receives an input/output request from a host device.

CONSTITUTION: When an input/output request is transferred to an electronic disk processor through a signal line 1 through an input/output device from a central processing unit, a host interface part G receives its request. In the case a load of the processor is heavy, and a signal of an input/output request registration load is inputted from a signal line 8, the host interface part G does not register the received request in its own interface part but transfers it to a transfer part H through a signal line 6. In this case, since a transfer instructing signal is inputted already from a signal line 9, the transfer part H transfers the received input/output request to the other electronic disk processor by a signal line 5. Subsequently, the transfer part H of the other electronic disk processing part receives the input/output request from the signal line 5, and transfers it to a subordinate interface part J through a signal line 7.