An exemplary information storage system of the present invention includes a plurality of information storage nodes and an administration node. The administration node determines the defined number of information storage nodes for storing the data having the identical content to each of received data. The received data belong to the defined number of categories, respectively. In a case where use of a first information storage node in the plurality of information storage nodes is interrupted, each storage node replicates the data of an identical content to data stored in the first information storage node whose category is pre-associated with a category of the data stored in the first information storage node to an information storage node selected according to a predetermined sequence.