Book Image

Hadoop Beginner's Guide

Book Image

Hadoop Beginner's Guide

Overview of this book

Data is arriving faster than you can process it and the overall volumes keep growing at a rate that keeps you awake at night. Hadoop can help you tame the data beast. Effective use of Hadoop however requires a mixture of programming, design, and system administration skills."Hadoop Beginner's Guide" removes the mystery from Hadoop, presenting Hadoop and related technologies with a focus on building working systems and getting the job done, using cloud services to do so when it makes sense. From basic concepts and initial setup through developing applications and keeping the system running as the data grows, the book gives the understanding needed to effectively use Hadoop to solve real world problems.Starting with the basics of installing and configuring Hadoop, the book explains how to develop applications, maintain the system, and how to use additional products to integrate with other systems.While learning different ways to develop applications to run on Hadoop the book also covers tools such as Hive, Sqoop, and Flume that show how Hadoop can be integrated with relational databases and log collection.In addition to examples on Hadoop clusters on Ubuntu uses of cloud services such as Amazon, EC2 and Elastic MapReduce are covered.
Table of Contents (19 chapters)
Hadoop Beginner's Guide
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Time for action – the replication factor in action


Let's repeat the preceding process, but this time, kill two DataNodes out of our cluster of four. We will give an abbreviated walk-through of the activity as it is very similar to the previous Time for action section:

  1. Restart the dead DataNode and monitor the cluster until all nodes are marked as live.

  2. Pick two DataNodes, use the process ID, and kill the DataNode processes.

  3. As done previously, wait for around 10 minutes then actively monitor the cluster state via dfsadmin, paying particular attention to the reported number of under-replicated blocks.

  4. Wait until the cluster has stabilized with an output similar to the following:

    Configured Capacity: 61032370176 (56.84 GB)
    Present Capacity: 45842373555 (42.69 GB)
    DFS Remaining: 44294680576 (41.25 GB)
    DFS Used: 1547692979 (1.44 GB)
    DFS Used%: 3.38%
    Under replicated blocks: 125
    Blocks with corrupt replicas: 0
    Missing blocks: 0
    -------------------------------------------------
    Datanodes available...