---
title: Low concurrent rebalance
description: Describes what AutoOps detects and surfaces with the Low concurrent rebalance insight: Cluster concurrent rebalance is below the recommended value.
url: https://docs-v3-preview.elastic.dev/elastic/autoops-insights/tree/main/elasticsearch/low_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
---

# Low concurrent rebalance
Cluster concurrent rebalance is below the recommended value. Shard moves proceed slowly when disks are uneven.
<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, configuration, 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 |
|--------------------------------------|---------|---------|
| Minimum 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 below the recommended minimum


#### What was detected

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

#### Recommendations

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

<dropdown title="Increase concurrent rebalance limit">
  **Condition**: Always shown for this insight.`cluster.routing.allocation.cluster_concurrent_rebalance` controls how many shards rebalance at once. Raise it with the action below to finish rebalancing sooner.
  ```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.
If the value is too low, the cluster cannot move shards quickly off a nearly full disk to nodes with more space. Disks might keep filling until flood stage, when indices become read-only. Some nodes might be cannot allocate shards, which can turn the cluster yellow or red and block writes to affected indices.

## Guide

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