'Find the replication destination associated with secondary.
:param api: Dell SCApi
:param secondary: String indicating the secondary to failover to.
:return: Destination SSN for the given secondary.'

def _parse_secondary(self, api, secondary):

    LOG.debug('_parse_secondary.    Looking    for    %s.', secondary)
    destssn = None
    for backend in self.backends:
        ssnstring = backend['target_device_id']
        if ((not secondary) or (secondary == ssnstring)):
            ssn = int(ssnstring)
            try:
                if api.find_sc(ssn):
                    destssn = ssn
                    break
            except exception.VolumeBackendAPIException:
                LOG.warning('SSN    %s    appears    to    be    down.', ssn)
    LOG.info('replication    failover    secondary    is    %(ssn)s', {'ssn': destssn})
    return destssn
