how to make website, use distributed file system- hadoop for data management

I am naive in big data technology, and have curiosity to relate it with the conventional application development.

The conventional way to develop any web application is to have a hosting server (or application server) and a database to manage the data. But lets say, I have a huge data set which is generated by the website, (i.e. GBs per second), then the website will fall into the category of managing big data.

lets suppose, I have a cluster of 20 computers, with 200GB of hard drives and core i3 processor. So now I will have enough processing and storage power for the website. (of-course hadoop is scalable too, if I need more resources). how to setup application server, to host the website in this cluster ? will I need load balancers for my application server since there is higher velocity, of http request to the application server? can anyone please guide ! thanks in advance.