I am not sure where we are in disagreement. I said that the MBPS is correlated with capacity (and drive count). You said that drive count is fundamentally limited by the controller. If I was in the fireman business I would say that we have two variables: diameter of the hose and amount of water available. It would be strange to say a fireman couldn't prevent a burned down house because of the causal relation of the diameter of the hose and not the amount of water available. That said, I try to be careful, while still writing to lay-people, about the causation-correlation link. I believe there are probably other more fundamental variables than capacity. But, to some extent, who cares? If you are in a windowless building, and can only see the people entering through the door, a good way to check if it is raining is by counting how many come in with umbrellas. Imagine me and a co-worker are walking outside in this situation. I say, “I need to grab an umbrella.” They retort, “but there is no causation between an umbrella and rain.” I would probably tell them “good luck with that” and still grab my umbrella because it is a really good indicator of what awaits - rain. A good indicator is what we are trying to find here - even without causation.

Clusterstock is like the New York Post of financial news. It is good for a funny headline and will maybe point out something interesting (but get the analysis completely wrong), so are you surprised?