Cosmo-b fans oscillating under even workload.

[leftwo]

While running a write workload to all disks in a cosmo-b we noticed that the fans will oscillate up and down.
The fan speed will vary between 4500 and 5500 RPMs. We have even seen a spike of higher numbers that then return back to the baseline.

[leftwo]

A CSV log of humility dashboard is here: /staff/core/hubris-2327/dashboard-mb1.csv

[cbiffle]

Can confirm this is happening pretty consistently in the office rn but appears to mostly affect one machine, which is weird. They all use the same PID coefficients.

It kinda sounds like the I term might be too large, though it could also be too-large P or too-small D because PID isn't terribly orthogonal.