Book Image

Real-time Analytics with Storm and Cassandra

By : Shilpi Saxena
Book Image

Real-time Analytics with Storm and Cassandra

By: Shilpi Saxena

Overview of this book

Table of Contents (19 chapters)
Real-time Analytics with Storm and Cassandra
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Replication in Cassandra and strategies


Replicating means to create a copy. This copy makes the data redundant and thus available even when one node fails or goes down. In Cassandra, you have the option to specify the replication factor as part of the creation of the keyspace or to later modify it. Attributes that need to be specified in this context are as follows:

  • Replication factor: This is a numeric value specifying the number of replicas

  • Strategy: This could be simple strategy or topology strategy; this decides the placement of replicas across the cluster

Internally, Cassandra uses the row key to store replicas or copies of data across various nodes on the cluster. A replication factor of n means there are n copies of data stored on n different nodes. There are certain rules of thumb with replication, and they are as follows:

  • A replication factor should never be more than the number of nodes in a cluster, or you will run into exceptions due to not enough replicas and Cassandra will start...