Hi all, What is UPS input load and how can that affect the power draw of devices plugged into it?
Context: I have an Eaton UPS. Into it I plugged TP Link smart plug to measure how much my homelab draws (1 truenas server, 1 rpi and a switch). These draw about ~29 W when under low to medium load. Almost every day (different time) for couple of hours, however, the plug measure about 6-7 Watts more (~36 W). I have checked both linux devices and they were doing basically nothing. Then I looked into TrueNAS monitoring and noticed that the start and end of each event is exactly the same time when UPS input load is increased from 0 % to ~6 %.
What is this UPS input load and how is it possible it affects measurements by a device that is plugged into it (the UPS) - NOT the other way around? Thank you
UPS devices normally uses wall (input) power, and switches to battery when input voltage is out of the target thresholds. So, input.load should represent the percentage of current wall power (in VA) relative to UPS’s max rated input power (VA). If your devices uses more power, input power from wall should increase as well.
If it’s peaking in certain times, it could be due some scheduled job temporarily increase CPU frequency, or automated tasks like file system snapshot might power-up/spin drives longer than regular usage.
Ahaa, so what you are saying that me seeing the input load on UPS is not the cause of the measured power consumption but just a “symptom”. That something (be it TrueNAS/rpi/switch) really draws more. How can I do a thorough analysis of what the devices do? Normally I check logs and htop and see they are just chilling. I check cpu, i/o and network and I thought that it should be pretty good indicator of if something is happening. Especially when its 6 Watts more thats like whole another rpi 😀
I don’t think its rpi or network switch, unless you’ve overclocked rpi with liquid nitrogen 😅. So, I assume its TrueNas device.
If it were a significant power difference, say 20-30 watts, you could easily find the process using htop/iotop. However, 6 watt difference is a relatively small value for a device with ~25 watts of idle power . It might be a process using just 1% system resources. That’s why I would look for systemd timers, cronjobs etc. to find scheduled tasks on specific times. Another possibility is automated S.M.A.R.T. self-tests. Those tests don’t show up in htop or iotop.