1. A storage apparatus being coupled to other storage apparatuses in a cluster system, the storage apparatus comprising: storage devices being configured to store a plurality of content data; and a processor being configured to: manage the plurality of content data, each content data is associated with a metadata which includes a data protection level as a data protection policy, and enforce the data protection policy to each content data by maintaining the number of copies of each content data in the cluster system, the number of copies of each content data determined based on the data protection level in the associated metadata, respectively.