Automate Fan power consumption table

[ErwanAliasr1]

Some BMCs like Dell or HPE, have a mode to force the fan speed at a given speed (usually in percentage of the pwm).

By keeping hwbench in idle mode, and forcing the fan speed, we can easily see a link between the fan speed and the power consumption. This could be used to reverse the power consumption of fans by following the delta of the PSUs/PDUs.

This could generate a table of the fan power consumption at a given speed and be reused by hwbench to create some "computed" fan power consumption metrics.

Here come a visualisation of this action done manually :

Automating this in a specific engine could ease the reverse of the fan's power consumption as vendors do not share this information easily.

[Arno500]

After a quick investigation:

• on Dell's iDRAC: PATCH https://<bmc host>/redfish/v1/Managers/System.Embedded.1/Attributes contains ThermalSettings.1.MinimumFanSpeed that can override the minimum fan speed, but not make it below what the algorithm decides
• on HPE's side, same idea: PATCH https://<bmc host>/redfish/v1/Chassis/1/Thermal with a structure like:

{
    "Oem": {
        "Hpe": {
            "FanPercentMinimum":20
        }
    }
}