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Hadoop 2.x Administration Cookbook

You're reading from   Hadoop 2.x Administration Cookbook Administer and maintain large Apache Hadoop clusters

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Product type Paperback
Published in May 2017
Publisher Packt
ISBN-13 9781787126732
Length 348 pages
Edition 1st Edition
Tools
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Author (1):
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Aman Singh Aman Singh
Author Profile Icon Aman Singh
Aman Singh
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Toc

Table of Contents (14) Chapters Close

Preface 1. Hadoop Architecture and Deployment FREE CHAPTER 2. Maintaining Hadoop Cluster HDFS 3. Maintaining Hadoop Cluster – YARN and MapReduce 4. High Availability 5. Schedulers 6. Backup and Recovery 7. Data Ingestion and Workflow 8. Performance Tuning 9. HBase Administration 10. Cluster Planning 11. Troubleshooting, Diagnostics, and Best Practices 12. Security Index

Initiating Namenode saveNamespace

In our earlier recipes, we have configured the Hadoop cluster and have gone through various concepts on cluster operations. We saw that Namenode stores the metadata, which is a combination of the fsimage file and edits file and these two images are never merged by Namenode, unless it is restarted or there is some other node, such as Secondary Namenode, which does this. We will be covering Secondary Namenode in this chapter at a later stage.

Whenever the Namenode is started, it applies all the changes in the edits file to the fsimage file and starts with a clean edits file. Depending upon the size of the edits log, it could take a long time to start up Namenode and this adds to the total time a Namenode stays in the safemode. Safemode, as discussed in the earlier chapters, is not just a factor of edits file size, but also of the time taken to build up the bitmap, which is a mapping of blocks to the Datanodes.

Note

If the edits file cannot be applied to the...

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