The controller unit carries out I/O accesses to and from {HEAD ~ the disk devices} via the intermediary devices based on access requests sent from {TAIL ~ host apparatus} 
The controller unit carries out I / O accesses to and from { HEAD ~ the disk devices } via the intermediary devices based on access requests sent from { TAIL ~ host apparatus }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL