A distributed storage system includes a plurality of storage nodes including: a storage device for storing data in such a way that the data can be written thereto and read therefrom; a memory in which a software program is recorded; and a CPU for executing the software program. The memory stores group management information in which a group configured with a plurality of storage nodes and the storage nodes that configure the group are associated with each other and recorded. The CPU converts data into a plurality of data blocks so that the data is redundant at a predetermined data protection level, and stores the data blocks into each of a plurality of storage nodes belonging to the same group based on the group management information.