QNAP offers Smart Fan control on their NAS with 3 preset fan mode: Quiet, Normal, and performance. There is not much customization available except that we are able to manually set a low temperature threshold where the fan would run at low speed when the temperature is below the set value and the full speed when the temperature is above the set value. The range of temperature is between from 35 to 44 ºC and it is referring to the system temperature and not the processor temperature.
On the TS-435, the default setting worked out quite well as the unit idle at low temperature of 29ºC with fan running at 900 rpm. When the system is transcoding with 22% of CPU usage, the CPU temperature jumped to 48ºC but the system temperature still runs at 30ºC. Under 100% CPU usage, we noticed the processor goes up to 68ºC but the system still runs at 35ºC. Since the system temperature stayed relatively steady even under load, we never heard the fan kicks into higher RPM. Thus, the TS-453D noise level is near silent even under heavy load.
We like just how quiet the unit runs but would probably love to see a more control for the cooling performance so we can manage the CPU and the system temperature. Additionally, while the fan on the NAS runs super quiet, we feel the noise isolation on the NAS can be improved a little bit. Since the fan runs quiet, it is much easier to hear the hard drive noise coming out of the NAS. So, we would love to have better noise isolation and dampening so that the NAS would run at even quieter on our desk.