I was programmatically able to affect the speed of the fans in SC216E26-R1200UB chassis by sending the correct SES command, but not all speed codes are accepted. After I send a speed code, the fan goes back to the speed it was running a second or two later automatically. The firmware does not report the SES threshold values, so is it possible that, while the speed is programmable, the logic is hard-coded so that it is somehow overridden elsewhere?
Regarding the fan speed control, the expander chip on the backplane can do it. However, there is a minimum voltage or fan speed to maintain, or the fan stops spinning. The firmware will compare the speed with the default profile and return to the minimum fan speed to keep the fan spinning. The lowest fan speed will be around 4000 RPM.
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