performing data migration by {HEAD ~ the data migration node} from {TAIL ~ the first storage} to the second storage 
from
performing data migration by { HEAD ~ the data migration node } from { TAIL ~ the first storage } to the second storage
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH