Elasticsearch OpenSearch Replication

By Opster Team

Updated: Jun 27, 2023

| 1 min read

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Replication refers to storing a redundant copy of the data. OpenSearch creates one primary shard with a replication factor set to 1. Replicas never get assigned to the same node on which primary shards are assigned, which means you should have at least two nodes in the cluster to assign the replicas. If a primary shard goes down, the replica automatically acts as a primary shard.


What are replicas in OpenSearch used for?

Replicas are used to provide high availability and failover. A higher number of replicas is also helpful for faster searches.


Update replica count

PUT /api-logs/_settings?pretty
    "index" : {
        "number_of_replicas" : 2

Common problems

  • By default, new replicas are not assigned to nodes with more than 85% disk usage. Instead, Elasticsearch throws a warning.
  • Creating too many replicas may cause a problem if there are not enough resources available in the cluster. 

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