Resizing an OpenSearch Cluster
If you need to scale up an existing OpenSearch cluster to meet performance and other requirements, resize the cluster to change the node configuration for the cluster.
You can only scale up an OpenSearch cluster's node configuration settings, you can't scale down the node configuration settings.
When you resize a cluster, the cluster's search functionality is in read-only mode until the resize operation completes, see Cluster Patching and Resize Operations. This applies to all vertical and horizontal resize operations, except the operation to increase the data node storage. When you increase the storage for a data node during the resize operation, the search functionality stays in read/write mode. You can increase the data node storage setting only during a vertical resize operation in which no other settings are being adjusted.
Limitations and Considerations
Keep the following items in mind when resizing OpenSearch clusters.
When resizing to improve availability and resiliency, use Horizontally Resizing an OpenSearch Cluster.
When resizing to improve performance, use Vertically Resizing an OpenSearch Cluster.
When you horizontally resize an OpenSearch cluster, you might also want to vertically resize the cluster.
You should vertically resize an OpenSearch cluster before you horizontally resize the cluster.
The more data nodes that you configure for an OpenSearch cluster, the more of an impact it will have on the cluster's performance.
During the resize process, an OpenSearch cluster's performance maybe impacted.