This categorization can be based on dividing the requests between {TAIL ~ write} and read requests, or between {HEAD ~ requests} that alter data stored on the storage device and requests that do not alter data on the storage device 
This categorization can be based on dividing the requests between { TAIL ~ write } and read requests , or between { HEAD ~ requests } that alter data stored on the storage device and requests that do not alter data on the storage device
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH