This NAS, a lenovo ix4-300d, came with Seagate drives (ST1000DM003), so its whatever the SMART 240 counter (Head flying hours) means to Seagate I guess. I just interpret it as "not parked", so it could be doing anything, but this NAS is not doing huge amounts of I/O - mostly just for music, movies, and some personal files. I think all the heads for all platters are on one assembly so they are either all parked or all spinning.