ZFS uses a log-structured filesystem journal, and in my experience can do a little less than twice as many 'random' writes to a spinning hard drive than that ha

ZFS uses a log-structured filesystem journal, and in my experience can do a little less than twice as many 'random' writes to a spinning hard drive than that hard drive is capable of. Of course the random writes are actually sequential. If you have a SSD log device configured, writes greater than 128k (IIRC) are sent directly to disk for performance reasons. This behavior is configurable and probably should be higher for modern SSDs... but anyway it's a neat idea that has been used in practice.