In a few prior posts, I mentioned that I replaced the soundproof cabinet's exhaust fans with quieter ones and added a temperature controller for the fans' speed. I sized the new fans well...much quieter, and they can handle the steady state heat extraction when the cluster is running at full power. However, what I didn't account for was heating of the room. The cluster is in a small office, and the office heats up after a few hours at full power. This makes sense...it's thermally equivalent to leaving a 1500W space heater on for hours/days. The reason that's a problem is that the inlet air is now hotter, which causes the exhaust to be even hotter, which causes the inlet air to be hotter, etc. The cabinet has a barrier between the outlet and inlet (both on the bottom of the cabinet) to minimize re-circulation, but if the whole room is hot, that doesn't matter. Leaving the door fully open and putting a large fan in the doorway seems to help some. It also offsets the house's gas heating needs, especially for the upper floor (where the office is). However, it's still getting too hot inside the room and cabinet. I don't have a great solution for this yet...
1. Fix room heating problem
2. Replace ntpd with chronyd