1. A storage system storing a plurality of content data, and a plurality of original metadata and back-up metadata associated with the plurality of content data, the storage system comprising: a first node including a first processor; and a plurality of second nodes, each of which includes a second processor being configured to manage a first storage region storing one or more original metadata of the plurality of original metadata, and a second storage region storing one or more back-up metadata of the plurality of back-up metadata; wherein on receipt of a first query by the first node, the first processor is configured to issue a second query to each of the plurality of second nodes, wherein on receipt of the second query by each of the plurality of second nodes, the second processor of each of the plurality of second nodes is configured to search its own first storage region, without searching its own second storage region, for content data and/or metadata related to the second query, and provide result of the second query to the first node, and wherein the first processor in the first node is further configured to aggregate the result sent from each of the plurality of second nodes.