yes, that is the point as big flush instead of many small ones would take either the same or, usually, less time than cumulative time of small flushes because of IO ordering and probability of some writes hitting the same data block.
yes, that is the point as big flush instead of many small ones would take either the same or, usually, less time than cumulative time of small flushes because of IO ordering and probability of some writes hitting the same data block.