I’ve been seeing a few occasions where Neil J. Gunther’s Universal Scalability Law doesn’t seem to model all of the important factors in a system as it scales. Models are only models, and they’re not the whole truth, so they never match reality perfectly. But there appear to be a small number of cases where systems can actually scale a bit better than linearly over a portion of the domain, due to what I’ve been calling an “economy of scale.” I believe that the Universal Scalability Law might need a third factor (seriality, coherency, and the new factor, economy of scale). I don’t think that the results I’m seeing can be modeled adequately with only two parameters.
Here are two publicly available cases that appear to demonstrate this phenomenon: Robert Haas’s recent blog post on PostgreSQL, titled …
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