obtaining information by the data migration node, {HEAD ~ the information} identifying {TAIL ~ the first storage} and the second storage 
identifying
obtaining information by the data migration node , { HEAD ~ the information } identifying { TAIL ~ the first storage } and the second storage
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH