Include an introduction and a conclusion no matter which method you choose to structure the body of your essay. It is often helpful to write the introduction and conclusion after you have written the body of your paper. A good introduction will introduce your subject in a general fashion and then begin to narrow gradually, ending with your argument. Think of it as a map of the rest of your essay. The conclusion should return to the ideas with which you began your essay and restate your argument. It should leave your reader with a summary of your main points as well as your argument.
One of the major benefits of using Hadoop in contrast to other distributed systems is its flat scalability curve. Executing Hadoop on a limited amount of data on a small number of nodes may not demonstrate particularly stellar performance as the overhead involved in starting Hadoop programs is relatively high. Other parallel/distributed programming paradigms such as MPI (Message Passing Interface) may perform much better on two, four, or perhaps a dozen machines. Though the effort of coordinating work among a small number of machines may be better-performed by such systems, the price paid in performance and engineering effort (when adding more hardware as a result of increasing data volumes) increases non-linearly.