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Replication factors in Aiven for OpenSearch®

The replication factor in Aiven for OpenSearch® determines the number of copies (replicas) of each index shard, which ensures data availability and prevents data loss.

The number_of_replicas is an index-level setting that defines how many replicas each primary shard has. By default, it is set to 1, meaning each shard has one replica for redundancy. You can configure this when creating or updating an index in the OpenSearch Dashboard.

Automatic replication factor adjustment​

Aiven for OpenSearch automatically adjusts replication factors in your indexes to maintain data availability.

  • The maximum number_of_replicas is the total number of nodes in your cluster minus one. This ensures that your data is replicated across all available nodes.

    Example: In a 3-node cluster, the maximum number_of_replicas is 2, which replicates all shards across the three nodes.

  • If you set number_of_replicas to 0 in a multi-node cluster, Aiven automatically increases it to 1. This ensures that your data remains available if one node fails.

Replication factor 0​

Setting the replication factor (number_of_replicas) to 0 means your data has no replicas. This reduces storage usage but significantly increases the risk of data loss if a node in the cluster fails.

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Enabling this setting comes with a reduced SLA, which must be agreed with your account manager.

When to use replication factor 0​

Consider using replication factor to 0 in the following scenarios:

  • Non-critical environments: Ideal for QA, testing, or development clusters where potential data loss doesn’t significantly impact operations.
  • Temporary data: Suitable when data can be recreated or is not critical, allowing you to save on storage costs.

Risks and considerations​

  • Data loss: Without replicas, a node failure can result in permanent data loss.
  • Manual recovery: If data loss occurs, data must be restored from snapshots manually, which can lead to downtime.
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  • In a scenario where a node fails before the first snapshot is taken, the system cannot recover the data. Aiven for OpenSearch automatically recreates the missing index, but the recreated index is empty.
  • In a normal node recovery scenario, Aiven for OpenSearch loads the latest snapshot to restore your data.

Set replication factor 0​

After agreeing to the reduced SLA, contact Aiven support to enable the option to set the replication factor (number_of_replicas) to 0. This allows you to configure your index without replicas.