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