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