 within each rectangle portion, after dividing data blocks into {HEAD ~ a plurality} of {TAIL ~ square portions}, allocating any remaining blocks to a partial portion; and 
within each rectangle portion , after dividing data blocks into { HEAD ~ a plurality } of { TAIL ~ square portions } , allocating any remaining blocks to a partial portion ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH