One of the issues with Hadoop is that after a MapReduce operation, the resulting files are written to the hard disk. Therefore, when there is a large data processing operation, there would be many read and write operations on the hard disk, which makes processing in Hadoop very slow. Moreover, the network latency, which is the time required to shuffle data between different nodes, also contributes to this problem. Another disadvantage is that one cannot make real-time queries from the files stored in HDFS. For machine learning problems, during training phase, the MapReduce will not persist over iterations. All this makes Hadoop not an ideal platform for machine learning.
A solution to this problem was invented at Berkeley University's AMP Lab in 2009. This came out of the PhD work of Matei Zaharia, a Romanian born computer scientist. His paper Resilient Distributed Datasets: A Fault-Tolerant Abstraction for In-Memory Cluster Computing (reference 4 in...
