opensearch-docs-cn/_opensearch/segment-replication/configuration.md

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---
layout: default
title: Segment replication configuration
nav_order: 12
parent: Segment replication
---
# 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/2229).
{: .warning }
To enable the segment replication type, reference the steps below.
## 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).