Next Generation Databases by Guy Harrison

Next Generation Databases by Guy Harrison

Author:Guy Harrison
Language: eng
Format: epub
Publisher: Apress, Berkeley, CA


Consistent Hashing

Cassandra and other dynamo-based databases distribute data throughout the cluster by using consistent hashing. The rowkey (analogous to a primary key in an RDBMS) is hashed. Each node is allocated a range of hash values, and the node that has the specific range for a hashed key value takes responsibility for the initial placement of that data.

In the default Cassandra partitioning scheme, the hash values range from -263 to 263-1. Therefore, if there were four nodes in the cluster and we wanted to assign equal numbers of hashes to each node, then the hash ranges for each would be approximately as follows:Node

Low Hash

High Hash



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