Working model of Mapreduce : Quick start guide for Mapreduce Programming
Map Reduce is a programming model by which large data set is processed in a parallel and distributed manner on a cluster .
This concept is first introduced by Google and later, it became part of Apache.
The processing unit of Mapreduce model is key-value pair. This model processes large data sets whether structured or unstructured and generates key-value pairs.
Generally Mapreduce consists of two phases.