Search icon CANCEL
Arrow left icon
Explore Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Conferences
Free Learning
Arrow right icon
Arrow up icon
GO TO TOP
Learning Hbase

You're reading from   Learning Hbase Learn the fundamentals of HBase administration and development with the help of real-time scenarios

Arrow left icon
Product type Paperback
Published in Nov 2014
Publisher
ISBN-13 9781783985944
Length 326 pages
Edition 1st Edition
Languages
Tools
Arrow right icon
Author (1):
Arrow left icon
Shashwat Shriparv Shashwat Shriparv
Author Profile Icon Shashwat Shriparv
Shashwat Shriparv
Arrow right icon
View More author details
Toc

Table of Contents (12) Chapters Close

Preface 1. Understanding the HBase Ecosystem FREE CHAPTER 2. Let's Begin with HBase 3. Let's Start Building It 4. Optimizing the HBase/Hadoop Cluster 5. The Storage, Structure Layout, and Data Model of HBase 6. HBase Cluster Maintenance and Troubleshooting 7. Scripting in HBase 8. Coding HBase in Java 9. Advance Coding in Java for HBase 10. HBase Use Cases Index

Reading and writing cycle


Now, let's see how the read-and-write operation takes place in HBase diagrammatically:

Let's discuss and understand how the read-and-write operation takes place in and from HBase tables. In HBase, the client does not write data to HFile directly; it is first written to WAL and then to HBase MemStore, which is shared by an HStore in the main memory and then flushed to HFile later. Refer to the following figure:

Write-Ahead Logs

Write-Ahead Logs facilitate the data reliability and reside on HDFS; each RegionServer hosts a single WAL. In the case of a RegionServer crash where MemStore is not flushed, WAL is used to restore the data to a new RegionServer. So, only once data is written successfully to WAL and MemStore, the write operation is said to be successful.

MemStore

MemStore acts as an in-memory write buffer with a default size of 64 MB. Once data in MemStore reaches the threshold (which is by default 40 percent of the heap size or 64 MB), it is flushed to a new HFile...

lock icon The rest of the chapter is locked
Register for a free Packt account to unlock a world of extra content!
A free Packt account unlocks extra newsletters, articles, discounted offers, and much more. Start advancing your knowledge today.
Unlock this book and the full library FREE for 7 days
Get unlimited access to 7000+ expert-authored eBooks and videos courses covering every tech area you can think of
Renews at €18.99/month. Cancel anytime