A disk array unit connected to {TAIL ~ a host unit} to give information thereto and receive {HEAD ~ information} therefrom 
A disk array unit connected to { TAIL ~ a host unit } to give information thereto and receive { HEAD ~ information } therefrom
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH