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