Just received this response from WD support:
By design, the internal fan of the My Cloud EX2 will remain at 0 RPM until the HDD temp reaches temperatures around 56°C, then there is an algorithm that will turn on the fan and increase/decrease according to the temperature. The HDD device operating max temperature is 65°C. If you see that the EX2 is reaching or surpassing these temperatures and the fan doesn’t come one, please let us know so we can assist you further.
Sincerely, [Deleted]
Western Digital Service and Support
Personal opinion: I do not want my drives running at 56 if I can help it. My little “AC Infinity AI-MPF80A Quiet 80mm USB Fan” from Amazon is still doing the trick and I will keep using it.
