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Monday, September 17, 2018

The reason why DB clustering need 3 nodes

Brief

Consider regarding database clustering consists of 3 nodes basically.

Database clustering which needs 3 nodes at least

  • Redis
  • MariaDB Galera Cluster
  • etcd
  • Consul
  • influxdb

Regarding distributed system, there is CAP theory.
  • Consistency
  • Availability
  • Partition Tolerance
In these features, Partition Tolerance is the biggest factor which defines the default number of database clustering.

If there were 3 nodes and split them, selected majority and continues to work.


If there were 4 nodes and split them, can not select majority and continue to work.
In the view of Partition Tolerance, database clustering needs 3 nodes at least. If increased nodes, the number of nodes would be odd number naturally.

Remark

There are database clustering which do not need.
  • Apache cassandra
  • Basho riak
  • Aerospike



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