Same issue here on a fresh 6.9.2 install with only 2 drives and 1 share:
Jul 11 19:09:02 Hannibal emhttpd: spinning down /dev/sdb
Jul 11 19:09:04 Hannibal emhttpd: spinning down /dev/sdc
Jul 11 19:12:23 Hannibal emhttpd: read SMART /dev/sdb
Jul 11 19:13:13 Hannibal emhttpd: read SMART /dev/sdc