When would you need multiple servers to host one web application?

Question by mik321g: When would you need multiple servers to host one web application?
Is that called “clustering” of servers? When a web request is sent, does it go through the main server, and if the main server can’t handle the extra load, then it forwards it to the secondary servers that can handle the load? Also, is one “server” that’s up and running the application called an “instance”?

Best answer:

Answer by Frederic
Clustering is one way to handle server load, but there are other reasons to use multiple servers, and in business, the general practice is to “stack” servers based on their purpose. For example, a large, busy web site might have this type of architecture:

* Front-end load balancer (Round-Robin director)
* Cluster of web servers (sub-domains, perhaps)
* Application servers (business logic processes that produce HTML sent to the web servers)
* Database servers (clustering or “grid” deployment to manage load)
* Storage servers (front end to SAN arrays)

Mind you, this is just a very high-level overview. But you can bet Fortune 500 companies use something along this line. Business web sites are much, much more than your “Mom ‘n Pop” web site!

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