A plurality of HDDs 12-1.about.12-n connected around a host 10 can be made to directly communicate with each other. For example, an HDD 12-1 makes another HDD to perform long distance seek using this communication line and measures the influence of vibration caused at that time. The measurement result is formed into a transfer function indicating the position change of the head of the relevant HDD against the operation of another HDD. An HDD is actually driven by a current value obtained by correcting the normal driving current of the driving motor of the head by the transfer function.