I have one Gen 2 and two Gen 3 drobos.
One of the G3s just redlighted a 6TB Toshiba HD. 
I powered down the drobo via the Dashboard and disconnected the USB cable. All four drives (2x4T, 2x6T) were hot, almost too hot to touch. The two 6T drives are 7200rpm Toshibas. I prefer 5400rpm HDs but that was all that I had access to.
In contrast, my G2 (4x4T) and other G3 (6x6T) were quite cool. (Why won’t Drobo include temperature sensors and readout alerts?) At this point, I’m suspecting fan failure. When the drobo is cool, I’ll pull the drives and check the fan operation.
I’ve seen a couple of other threads on fan replacement and want to know what the fan specs are for my drobos and what can replace and/or upgrade them. I’m aware that:
- the fan might not be bad in the one drobo and need not be replaced
- replacing the fan would void any warranty, if I had any.
My G2 is noisy, always has been; my G3s are not. So I’m interested in upgrading the fan for the G2 and maybe replacing one in one G3 and/or upgrading both G3s as well.
Any info on fan specs?