An analysis is made of a number of aspects of the buffering scheme during the merge phase of an external sort. A discussion is given of the problem of choosing between double buffering, complete single buffering, or something in between, assuming a constraint on the amount of internal memory available for buffering. It is shown that single buffering degrades processing time for a merge pass by an average of from 25% to 37%. It is shown that single buffering is faster than double buffering if and only if there is space available for fewer than 16 buffers.