Coming back to this after a break. The original situation, if you recall, was that my new build—running Proxmox with TrueNAS SCALE in a VM—was running a very hot CPU (60s C) even unloaded; I rebuilt it with more attention to the cooling, and there was no difference. As posted just above, I thought that “[t]he only sensible explanation would seem to be that I really badly fucked up the heatsink connection”, but I eventually gave up worrying about it.
Well, as discussed elsewhere, I decided to move my install from Proxmox to bare metal. This is complete; I’m running SCALE on the original machine.
And: temperatures are totally fine. In the 30s C unloaded. And this is reported by TrueNAS, by the sensors command, by IPMI; it’s not my imagination, or Proxmox mis-reporting the temperature.
I have no idea why it would be the case that Proxmox would run so vastly hotter. It’s true that I don’t have any VMs running on the SCALE build, but I was getting temperatures in the 60s on the Proxmox build even when completely unloaded.
So, I guess this is a good result, and I guess this is one more reason to be glad at having ditched Proxmox.