by Yanchang Zhao, RDataMining.com
The lectures in week 3 of a free online course Introduction to Data Science give an excellent introduction to MapReduce and Hadoop, and demonstrate with examples how to use MapReduce to do various tasks, such as, word frequency counting, matrix multiplication, simple social network analysis, and a join operation like in a relational database. There are also interesting comparisons with relational DB. The examples look simple, but they are scalable and can handle really Big Data. The course also introduces NoSQL systems.
Although the course has been closed, all lecture videos can be accessed via the “Preview” button on the course page at the above link.
They are definitely worth watching if you want to get some idea about MapReduce and Hadoop.