Hadoop

Hadoop is a framework for running large scale distributed applications. The Hadoop project develops open-source software for reliable, scalable, distributed computing. The Apache Hadoop software library is a framework that allows for the distributed processing of large data sets across clusters of computers using simple programming models.

It is designed to scale up from single servers to thousands of machines, each offering local computation and storage. Rather than rely on hardware to deliver high-availability, the library itself is designed to detect and handle failures at the application layer, so delivering a highly-available service on top of a cluster of computers, each of which may be prone to failures.

Prerequisites

Supported Platforms

• GNU/Linux is supported as a development and production platform. Hadoop has been demonstrated on GNU/Linux clusters with 2000 nodes.
• Windows is also a supported platform but the followings steps are for Linux only. To set up Hadoop on Windows, see wiki page.

Required software for Linux include:

• Java™ must be installed. Recommended Java versions are described at HadoopJavaVersions.
• ssh must be installed and sshd must be running to use the Hadoop scripts that manage remote Hadoop daemons.

Modules

• Hadoop Common: The common utilities that support the other Hadoop modules.
• Hadoop Distributed File System (HDFS™): A distributed file system that provides high-throughput access to application data.
• Hadoop YARN: A framework for job scheduling and cluster resource management.
• Hadoop MapReduce: A YARN-based system for parallel processing of large data sets.

Who Uses Hadoop?

A wide variety of companies and organizations use Hadoop for both research and production. Users are encouraged to add themselves to the Hadoop PoweredBy wiki page.

Components of Hadoop

The core components in the first iteration of Hadoop were MapReduce, the Hadoop Distributed File System (HDFS) and Hadoop Common, a set of shared utilities and libraries. As its name indicates, MapReduce uses map and reduce functions to split processing jobs into multiple tasks that run at the cluster nodes where data is stored and then to combine what the tasks produce into a coherent set of results. MapReduce initially functioned as both Hadoop's processing engine and cluster resource manager, which tied HDFS directly to it and limited users to running MapReduce batch applications.

Hadoop applications and use cases

Hadoop is primarily geared to analytics uses, and its ability to process and store different types of data makes it a particularly good fit for big data analytics applications. Big data environments typically involve not only large amounts of data, but also various kinds, from structured transaction data to semistructured and unstructured forms of information, such as internet clickstream records, web server and mobile application logs, social media posts, customer emails and sensor data from the internet of things (IoT).