https://electronics.stackexchange.com/a/65827
> A mosfet needs a certain voltage at its gate to turn fully on. 8V is a typical value. A simple driver circuit could get this voltage directly from the power that also feeds the motor. When this voltage is too low to turn the mosfet fully on a dangerous situation (from the point of view of the moseft) can arise: when it is half-on, both the current through it and the voltage across it can be substantial, resulting in a dissipation that can kill it. Death by undervoltage.
That said, I'm not an electronics engineer, so my understanding might not be entirely accurate. It’s possible that the degradation was caused by power fluctuations rather than the power cap itself, or perhaps another factor was at play.
[1] https://electronics.stackexchange.com/questions/65837/can-el... [2] https://superuser.com/questions/1202062/what-happens-when-ha...
Volts is as supplied by the utility company.
Amps are monitored per rack and the usual data centre response to going over an amp limit is that a fuse blows or the data centre asks you for more money!
The only way you can decrease power used by a server is by throttling the CPUs.
The normal way of throttling CPUs is via the OS which requires cooperation.
I speculate this is possible via the lights out base band controller (which doesn't need the os to be involved), but I'm pretty sure you'd see that in /sys if it was.
I don't know for sure how the limiting is done, but a simple circuit breaker like the ones we have in our houses would be a simple solution for it. That causes the rack to loose power when the circuit breaks, which is not ideal because you loose the whole rack and affect multiple customers.
Another option would be a current/power limiter[0], which would cause more problems because P = U * I. That would make the voltage (U) drop and then the whole system to be undervolted - weird glitches happen here and it's a common way to bypass various security measures in chips. For example, Raspberry Pi ran this challenge [1] to look for this kind of bugs and test how well their chips can handle attacks, including voltage attacks.
[0] - https://en.m.wikipedia.org/wiki/Current_limiting [1] - https://www.raspberrypi.com/news/security-through-transparen...
No idea what the article is talking about with the damage. Computers like to run slow when possible. There's basically no downside except they take longer to do things.
Can anyone elaborate on this point? This is counter to my intuition (and in fact, what I saw upon a cursory search), which is that power capping should prolong the useful lifetime of various components.
The only search results I found that claimed otherwise were indicating that if you're running into thermal throttling, then higher operating temperatures can cause components (e.g. capacitors) to degrade faster. But that's expressly not the case in the article, which looked at various temperature sensors.