'Gets LUN from cache table.
Refreshes cache if LUN not found in cache.'

def _get_lun_from_table(self, name):

    lun = self.lun_table.get(name)
    if (lun is None):
        lun_list = self.zapi_client.get_lun_list()
        self._extract_and_populate_luns(lun_list)
        lun = self.lun_table.get(name)
        if (lun is None):
            raise exception.VolumeNotFound(volume_id=name)
    return lun
