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