Book Image

Hadoop 2.x Administration Cookbook

By : Aman Singh
Book Image

Hadoop 2.x Administration Cookbook

By: Aman Singh

Overview of this book

Hadoop enables the distributed storage and processing of large datasets across clusters of computers. Learning how to administer Hadoop is crucial to exploit its unique features. With this book, you will be able to overcome common problems encountered in Hadoop administration. The book begins with laying the foundation by showing you the steps needed to set up a Hadoop cluster and its various nodes. You will get a better understanding of how to maintain Hadoop cluster, especially on the HDFS layer and using YARN and MapReduce. Further on, you will explore durability and high availability of a Hadoop cluster. You’ll get a better understanding of the schedulers in Hadoop and how to configure and use them for your tasks. You will also get hands-on experience with the backup and recovery options and the performance tuning aspects of Hadoop. Finally, you will get a better understanding of troubleshooting, diagnostics, and best practices in Hadoop administration. By the end of this book, you will have a proper understanding of working with Hadoop clusters and will also be able to secure, encrypt it, and configure auditing for your Hadoop clusters.
Table of Contents (20 chapters)
Hadoop 2.x Administration Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface
Index

Promoting Secondary Namenode to Primary


In this recipe, we will cover how to promote Secondary Namenode to be Primary Namenode.

In production, Datanodes will never talk to the Secondary and only the Primary node knows about the data block mappings. In a non-HA setup, if the Primary Namenode fails, there will be outage, but we can still reduce the downtime by quickly promoting the Secondary to be Primary.

Getting ready

For this recipe, make sure you have completed the previous recipe on Secondary Namenode configuration and have a running Secondary Namenode.

How to do it...

  1. Connect to the master2.cyrus.com master node and switch to user hadoop.

  2. The first thing is to check the seen_txid file under location /data/secondary/current/, to make sure until what point is the Secondary in sync with Primary.

  3. If the lag is high, it is important that the metadata is copied from the NFS mount of the Primary Namenode. That is the reason of having at least one Primary Namenode metadata directory mount on NFS.

  4. Change...