What's the difference between "Layers" and "Tiers"?

architecture
cretzel picture cretzel · Sep 23, 2008 · Viewed 135k times · Source

What's the difference between "Layers" and "Tiers"?

Answer

Panos picture Panos · Sep 23, 2008

Logical layers are merely a way of organizing your code. Typical layers include Presentation, Business and Data – the same as the traditional 3-tier model. But when we’re talking about layers, we’re only talking about logical organization of code. In no way is it implied that these layers might run on different computers or in different processes on a single computer or even in a single process on a single computer. All we are doing is discussing a way of organizing a code into a set of layers defined by specific function.

Physical tiers however, are only about where the code runs. Specifically, tiers are places where layers are deployed and where layers run. In other words, tiers are the physical deployment of layers.

Source: Rockford Lhotka, Should all apps be n-tier?

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