---
title: High concurrent rebalance
description: Describes what AutoOps detects and surfaces with the High concurrent rebalance insight: Cluster concurrent rebalance is above the recommended value.
url: https://docs-v3-preview.elastic.dev/elastic/autoops-insights/tree/main/elasticsearch/high_concurrent_rebalance
products:
  - Elastic Cloud Enterprise
  - Elastic Cloud Hosted
  - Elastic Cloud on Kubernetes
  - Elasticsearch
applies_to:
  - Elastic Cloud Hosted: Generally available
  - Elastic Cloud on Kubernetes: Generally available
  - Elastic Cloud Enterprise: Generally available
  - Self-managed Elastic deployments: Generally available
---

# High concurrent rebalance
Cluster concurrent rebalance is above the recommended value. Many shards might relocate at once.
<note>
  For a complete list of insights, refer to [AutoOps insights](https://docs-v3-preview.elastic.dev/elastic/autoops-insights/tree/main/elasticsearch).
</note>


## Insight details


| Field     | Value                         |
|-----------|-------------------------------|
| Component | Elasticsearch                 |
| Severity  | Medium                        |
| Scope     | Cluster                       |
| Domains   | performance, shard-allocation |


## Customization settings

You can customize these settings to adjust when AutoOps detects this event and presents the insight. Refer to [AutoOps event settings](https://docs-v3-preview.elastic.dev/elastic/docs-content/tree/main/deploy-manage/monitor/autoops/ec-autoops-event-settings) for details.
The default customization settings are:

| Setting                              | Type    | Default |
|--------------------------------------|---------|---------|
| Maximum cluster concurrent rebalance | Integer | `2`     |


## Example: What you might see in AutoOps

The following is an example of what you might see when this insight is triggered. Real insights use live data and links from your deployment or cluster.

### Cluster concurrent rebalance is above the recommended maximum


#### What was detected

`cluster.routing.allocation.cluster_concurrent_rebalance` is 12. Recommended maximum: 2.

#### Recommendations

<note>
  AutoOps shows different recommendations depending on how their conditions match your deployment or cluster.
</note>

<dropdown title="Decrease concurrent rebalance limit">
  **Condition**: Always shown for this insight.High concurrent rebalance can overload the cluster. Lower `cluster.routing.allocation.cluster_concurrent_rebalance` with the action below.
  ```json

  {
    "persistent": {
      "cluster.routing.allocation.cluster_concurrent_rebalance": 2
    }
  }
  ```

  <note>
    Requires the `manage cluster` privilege. Requires Elasticsearch 8.0.0 or later. This action changes cluster or index configuration.
  </note>
</dropdown>


#### Background and impact

This setting caps how many shards the cluster can move at once to rebalance shard distribution across nodes, while respecting allocation filters and forced awareness.
When shards move, both the sending and receiving nodes need disk and network capacity. If concurrent rebalance is too high, the cluster might consume too many resources at once during relocation. That can slow indexing and search while moves are in progress.

## Guide

[Cluster level shard allocation routing settings](https://docs-v3-preview.elastic.dev/elastic/elasticsearch/tree/main/reference/elasticsearch/configuration-reference/cluster-level-shard-allocation-routing-settings)