Currently we cannot fill the 19" rack completely. So we have 12 GPU nodes, 2U each. The 42U rack is connected to a cooling unit that blows cold air in front of the computers, sucking in hot air from behind. As far as I understood this thread, the best practice is to stack all nodes without leaving any gaps in between and to use blank panels to close all empty slots.
Now where in the rack should I put this 24U stack of hot computers? All at the bottom, to let the cool air sink to the lowest node? All to the top, because the wind flow is strong enough? Somewhere in the middle?