Basically, the way it works is:

    No change to Submitting, Reading, and Deleting files.

    So if the replication type is xyz

    ColumnMeaning
    xnumber of replica in other data centers
    ynumber of replica in other racks in the same data center
    znumber of replica in other servers in the same rack

    Now when requesting a file key, an optional "dataCenter" parameter can limit the assigned volume to the specific data center. For example, this specify