A server apparatus that stores a content acquired from a client device in a storage unit, said server apparatus comprising: a content segment acquisition unit configured to sequentially acquire, from the client device, comparison counterpart segments constituting a part of one candidate content of a plurality of candidate contents, the comparison counterpart segments respectively corresponding to one of a plurality of comparison segments constituting a part of one or more already acquired contents stored in the storage unit; a duplication decision unit configured to compare, each time said content segment acquisition unit acquires the comparison counterpart segment, the comparison counterpart segment and the comparison segment corresponding to the comparison counterpart segment, to thereby decide whether a content including the comparison segment that agrees with the comparison counterpart segment is present among the already acquired contents; and a content acquisition unit configured to acquire the candidate content from the client device and store the candidate content in the storage unit in the case where said duplication decision unit decides that a content including the comparison segment that agrees with the comparison counterpart segment is not present among the already acquired contents, wherein said content segment acquisition unit is configured to abort acquisition of a subsequent comparison counterpart segment of the candidate content, in the case where said duplication decision unit decides that a content including the comparison segment that agrees with the comparison counterpart segment is not present among the already acquired contents, characterized in that a priority is given in advance to each of the plurality of candidate contents, and in that said content segment acquisition unit is configured to preferentially acquire the comparison counterpart segment of the candidate content having a higher priority among the plurality of candidate contents, wherein said duplication decision unit is further configured to (i) decide, in the case where said duplication decision unit decides that a content including the comparison segment that agrees with the comparison counterpart segment is present among the already acquired contents, whether a content including more than one comparison segment that agrees with more than one of the plurality of comparison counterpart segments is present among the already acquired contents, and (ii) degrade the priority of the candidate content from the priority given in advance, in the case where said duplication decision unit decides that the content including the more than one comparison segment that agrees with the more than one of the plurality of comparison counterpart segments is present among the already acquired contents. a content segment acquisition unit configured to sequentially acquire, from the client device, comparison counterpart segments constituting a part of one candidate content of a plurality of candidate contents, the comparison counterpart segments respectively corresponding to one of a plurality of comparison segments constituting a part of one or more already acquired contents stored in the storage unit; a duplication decision unit configured to compare, each time said content segment acquisition unit acquires the comparison counterpart segment, the comparison counterpart segment and the comparison segment corresponding to the comparison counterpart segment, to thereby decide whether a content including the comparison segment that agrees with the comparison counterpart segment is present among the already acquired contents; and a content acquisition unit configured to acquire the candidate content from the client device and store the candidate content in the storage unit in the case where said duplication decision unit decides that a content including the comparison segment that agrees with the comparison counterpart segment is not present among the already acquired contents, wherein said content segment acquisition unit is configured to abort acquisition of a subsequent comparison counterpart segment of the candidate content, in the case where said duplication decision unit decides that a content including the comparison segment that agrees with the comparison counterpart segment is not present among the already acquired contents, characterized in that a priority is given in advance to each of the plurality of candidate contents, and in that said content segment acquisition unit is configured to preferentially acquire the comparison counterpart segment of the candidate content having a higher priority among the plurality of candidate contents, wherein said duplication decision unit is further configured to (i) decide, in the case where said duplication decision unit decides that a content including the comparison segment that agrees with the comparison counterpart segment is present among the already acquired contents, whether a content including more than one comparison segment that agrees with more than one of the plurality of comparison counterpart segments is present among the already acquired contents, and (ii) degrade the priority of the candidate content from the priority given in advance, in the case where said duplication decision unit decides that the content including the more than one comparison segment that agrees with the more than one of the plurality of comparison counterpart segments is present among the already acquired contents.