I have had my replacement EX2 for over a week and I continue to monitor the zero RPM fan discussion. So far I have never seen the fan running (zero RPMs are always reported in the diagnostic window), not that it’s a problem; I’m just saying I have never seen the system report more than zero RPMs for the fan.
From the UI command console I ran the built-in NAS to USB backup utility copying about 800GB of data from one of the NAS’ shares to the USB (USB3) My Passport Ultra connected drive. The process took several hours (probably more than 4). For whatever reason, running a NAS to USB backup pegs the CPU at 100% for virtually the entire process and the EX2 really starts to heat up.
When the NAS is idle, both drives seem to hover around 38 - 40 degrees C, but while the NAS to USB backup was running, the CPU was pegged at 100% and both drives reported a temperature above 51 degrees C (about 124 degrees F). Even as the heat started to rise, the fan continued to report zero RPMs. To the touch, the drives seemed quite hot but maybe that is still within standard operating range. For reference, the ambient temperature of the room was 70 degrees F.
I have two questions:
Is it normal when running the built-in NAS to USB backup utility for the CPU to be pegged at 100%?
Could someone from WD tell us at what temperature the fan is programmed to start operating?