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86 changes: 86 additions & 0 deletions subfolder/configuration.md
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---
layout: default
title: Segment replication configuration
nav_order: 12
parent: Segment replication
grand_parent: Availability and Recovery
---

# Segment replication configuration

Segment replication is an experimental feature. Therefore, we do not recommend the use of segment replication in a production environment. For updates on the progress of segment replication or if you want to leave feedback that could help improve the feature, see the [Segment replication issue](https://github.com/opensearch-project/OpenSearch/issues/2194).
{: .warning }

To enable the segment replication type, reference the [steps below](#enable-on-a-node-using-a-tarball-install).

- [Seventh bad link](https://opensearch.org.org)

## Enabling the feature flag

There are several methods for enabling segment replication, depending on the install type. You will also need to set the replication strategy to `SEGMENT` when creating the index.

### Enable on a node using a tarball install

The flag is toggled using a new jvm parameter that is set either in `OPENSEARCH_JAVA_OPTS` or in config/jvm.options.

1. Option 1: Update config/jvm.options by adding the following line:

````json
-Dopensearch.experimental.feature.replication_type.enabled=true
````

1. Option 2: Use the `OPENSEARCH_JAVA_OPTS` environment variable:

````json
export OPENSEARCH_JAVA_OPTS="-Dopensearch.experimental.feature.replication_type.enabled=true"
````
1. Option 3: For developers using Gradle, update run.gradle by adding the following lines:

````json
testClusters {
runTask {
testDistribution = 'archive'
if (numZones > 1) numberOfZones = numZones
if (numNodes > 1) numberOfNodes = numNodes
systemProperty 'opensearch.experimental.feature.replication_type.enabled', 'true'
}
}
````

### Enable with Docker containers

If you're running Docker, add the following line to docker-compose.yml underneath the `opensearch-node` and `environment` section:

````json
OPENSEARCH_JAVA_OPTS="-Dopensearch.experimental.feature.replication_type.enabled=true" # Enables segment replication
````

### Setting the replication strategy on the index

To set the replication strategy to segment replication, create an index with replication.type set to `SEGMENT`:

````json
PUT /my-index1
{
"settings": {
"index": {
"replication.type": "SEGMENT"
}
}
}
````

## Known limitations

1. Enabling segment replication for an existing index requires [reindexing](https://github.com/opensearch-project/OpenSearch/issues/3685).
1. Rolling upgrades are currently not supported. Full cluster restarts are required when upgrading indexes using segment replication. [Issue 3881](https://github.com/opensearch-project/OpenSearch/issues/3881).
1. [Cross-cluster replication](https://github.com/opensearch-project/OpenSearch/issues/4090) does not currently use segment replication to copy between clusters.
1. Increased network congestion on primary shards. [Issue - Optimize network bandwidth on primary shards](https://github.com/opensearch-project/OpenSearch/issues/4245).
1. Shard allocation algorithms have not been updated to evenly spread primary shards across nodes.
1. Integration with remote-backed storage as the source of replication is [currently unsupported](https://github.com/opensearch-project/OpenSearch/issues/4448).

### Further resources regarding segment replication

1. [Known issues](https://github.com/opensearch-project/OpenSearch/issues/2194).
1. Steps for testing (link coming soon).
1. Segment replication blog post (link coming soon).
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---
layout: default
title: Segment replication
nav_order: 70
has_children: true
parent: Availability and Recovery
redirect_from:
- /opensearch/segment-replication/
- /opensearch/segment-replication/index/
---

# Segment replication

Segment replication is an experimental feature with OpenSearch 2.3. Therefore, we do not recommend the use of segment replication in a production environment. For updates on the progress of segment replication or if you want leave feedback that could help improve the feature, see the [Segment replication git issue](https://github.com/opensearch-project/OpenSearch/issues/2194).
{: .warning}

With segment replication, segment files are copied across shards instead of documents being indexed on each shard copy. This improves indexing throughput and lowers resource utilization at the expense of increased network utilization.

As an experimental feature, segment replication will be behind a feature flag and must be enabled on **each node** of a cluster and pass a new setting during index creation.
{: .note }

### Potential use cases

- Users who have high write loads but do not have high search requirements and are comfortable with longer refresh times.
- Users with very high loads who want to add new nodes, as you do not need to index all nodes when adding a new node to the cluster.

This is the first step in a series of features designed to decouple reads and writes in order to lower compute costs.
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- [See the FAQ](https://opensearch.org/faq)

## Why use OpenSearch?
<style>p{color:red;}</style>
<p>Witsh OpenSearch, you can prerform the following ushe cases.</p>

With OpenSearch, yoeu can prerform the following ushe cases. This is an addition to the PR.