'The only difference between this method and the replication policy
DiskFile method is passing in the frag_index and frag_prefs kwargs to
our manager\'s get_ondisk_files method.
:param files: list of file names'

def _get_ondisk_files(self, files):

    self._ondisk_info = self.manager.get_ondisk_files(files, self._datadir, frag_index=self._frag_index, frag_prefs=self._frag_prefs)
    return self._ondisk_info
