'Get specific volume details, from an RDF group.
:param array: the array serial number
:param rdf_number: the rdf group number
:param device_id: the device id'

def get_rdf_group_volume(self, array, rdf_number, device_id):

    resource_name = ('%(rdf)s/volume/%(dev)s' % {'rdf': rdf_number, 'dev': device_id})
    return self.get_resource(array, REPLICATION, 'rdf_group', resource_name)
