If {HEAD ~ the number n} of {TAIL ~ the requests} being processed is less than 2 , control is passed to step 14, the LBA as a median point of the logical block address LBA of the disk devices 13 and 14 is calculated, and the obtained value is set as a boundary LBA 
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If { HEAD ~ the number n } of { TAIL ~ the requests } being processed is less than 2 , control is passed to step 14 , the LBA as a median point of the logical block address LBA of the disk devices 13 and 14 is calculated , and the obtained value is set as a boundary LBA
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH