The present invention makes it possible to preserve any and all update data relating to the updating of a storage device. The present invention is devised so that if a first storage device (3S) is updated by writing data into this first storage device, the update data relating to the updating of the first storage device is written into a second storage device (3D). The system (100) comprises an acquisition portion (15) that acquires a use rate of the second storage device and a threshold value for this use rate, an updating stopping portion (7) which judges whether or not the acquired use rate exceeds the threshold value, and which stops the updating of the second storage device if the result of this judgment is affirmative, and an updating-stop canceling portion (8) which cancels the stopping if it is detected that the use rate of the second storage device has decreased after the stopping has been performed.