Portion of {HEAD ~ data stream} or {TAIL ~ data block} 200 is to be stored in storage device 210, representing a storage device of a storage system  
Portion of { HEAD ~ data stream } or { TAIL ~ data block } 200 is to be stored in storage device 210 , representing a storage device of a storage system
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH