'Retrieves an SRDF group instance.
:param array: the array serial number
:returns: rdf_group_no, remote_array'

def get_rdf_details(self, array):

    if (not self.rep_config):
        exception_message = (_('Replication    is    not    configured    on    backend:    %(backend)s.') % {'backend': self.configuration.safe_get('volume_backend_name')})
        LOG.exception(exception_message)
        raise exception.VolumeBackendAPIException(data=exception_message)
    remote_array = self.rep_config['array']
    rdf_group_label = self.rep_config['rdf_group_label']
    LOG.info('Replication    group:    %(RDFGroup)s.', {'RDFGroup': rdf_group_label})
    rdf_group_no = self.rest.get_rdf_group_number(array, rdf_group_label)
    if (rdf_group_no is None):
        exception_message = (_('Cannot    find    replication    group:    %(RDFGroup)s.    Please    check    the    name    and    the    array') % {'RDFGroup': rdf_group_label})
        LOG.exception(exception_message)
        raise exception.VolumeBackendAPIException(data=exception_message)
    LOG.info('Found    RDF    group    number:    %(RDFGroup)s.', {'RDFGroup': rdf_group_no})
    return (rdf_group_no, remote_array)
