Having the same issue on 4 of my drives. It is def not the card or the cables because I tried replacing both and still the same issue. Also just replaced the MB and processor and issue still persists. It has to be software related and the unraid team really needs to look at this.
Jul 20 06:34:56 SkyRAID emhttpd: spinning down /dev/sdl
Jul 20 06:35:47 SkyRAID emhttpd: spinning down /dev/sdj
Jul 20 06:35:47 SkyRAID emhttpd: spinning down /dev/sdf
Jul 20 06:35:47 SkyRAID emhttpd: spinning down /dev/sdi
Jul 20 07:00:17 SkyRAID emhttpd: read SMART /dev/sdj
Jul 20 07:00:17 SkyRAID emhttpd: read SMART /dev/sdf
Jul 20 07:00:17 SkyRAID emhttpd: read SMART /dev/sdi
Jul 20 07:00:31 SkyRAID emhttpd: read SMART /dev/sdl
Jul 20 07:31:39 SkyRAID emhttpd: spinning down /dev/sdj
Jul 20 07:31:49 SkyRAID emhttpd: spinning down /dev/sdf
Jul 20 07:31:49 SkyRAID emhttpd: spinning down /dev/sdl
Jul 20 07:31:49 SkyRAID emhttpd: spinning down /dev/sdi
Jul 20 08:00:12 SkyRAID emhttpd: read SMART /dev/sdj
Jul 20 08:00:12 SkyRAID emhttpd: read SMART /dev/sdf
Jul 20 08:00:12 SkyRAID emhttpd: read SMART /dev/sdi
Jul 20 08:00:26 SkyRAID emhttpd: read SMART /dev/sdl