---
title: Cluster Concurrent Rebalance High
description: Describes what AutoOps detects and surfaces with the Cluster Concurrent Rebalance High insight: Cluster concurrent rebalance is set above the recommended value, so many shards might relocate at the same time.
url: https://docs-v3-preview.elastic.dev/elastic/autoops-insights/tree/main/elasticsearch/cluster_concurrent_rebalance_high
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
---

# Cluster Concurrent Rebalance High
Cluster concurrent rebalance is set above the recommended value, so many shards might relocate at the same time. Each move consumes disk and network on both source and destination nodes.
<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.

### The cluster concurrent rebalance setting is set to a higher value than recommended


#### What was detected

The current concurrent rebalance is set to: 12.
The recommended setting is: 12.

#### 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": 12
    }
  }
  ```

  <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

Impact: This could cause performance degradation due to disk and network load.
This setting determines the maximum number of shards the cluster can move at any one time to rebalance the distribution of shards across the nodes, obeying any existing shard allocation rules such as allocation filtering and forced awareness.
When shards are moved, resources are required on both nodes — the one sending the shard and the one receiving it. If the cluster concurrent rebalance is high, the cluster could use up too many resources at once when moving shards.