---
title: Minimum master nodes below quorum
description: Describes what AutoOps detects and surfaces with the Minimum master nodes below quorum insight: `discovery.zen.minimum_master_nodes` is set below a safe majority of master-eligible nodes.
url: https://docs-v3-preview.elastic.dev/elastic/autoops-insights/tree/main/elasticsearch/minimum_master_nodes_below_quorum
products:
  - Elastic Cloud Enterprise
  - Elastic Cloud on Kubernetes
  - Elasticsearch
applies_to:
  - Elastic Cloud on Kubernetes: Generally available
  - Elastic Cloud Enterprise: Generally available
  - Self-managed Elastic deployments: Generally available
---

# Minimum master nodes below quorum
`discovery.zen.minimum_master_nodes` is set below a safe majority of master-eligible nodes. On clusters that still use this legacy Zen discovery setting, that weakens protection against split brain if the cluster partitions.
<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  | High                                        |
| Scope     | Cluster                                     |
| Domains   | configuration, high-availability, stability |


## 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.

### Minimum master nodes setting is below quorum


#### What was detected

`discovery.zen.minimum_master_nodes` is es-data-01. The cluster has 12 master-eligible nodes.

#### Recommendations

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

<dropdown title="Set minimum master nodes quorum">
  **Condition**: Always shown for this insight.Set `discovery.zen.minimum_master_nodes` to 2 in each node's config, then rolling-restart master-eligible nodes so the quorum takes effect.
</dropdown>


#### Background and impact

`discovery.zen.minimum_master_nodes` is the legacy Zen discovery quorum setting. It applied on older Elasticsearch versions that used Zen Discovery to elect a master. Modern Elasticsearch uses automatic voting configuration instead, but this setting can still appear on upgraded clusters or legacy deployments.
When the value is below half of master-eligible nodes, rounded up, a network partition can let disconnected nodes form a second cluster with its own master. Split brain can cause conflicting writes and data loss.

## Guide

[Quorum-based decision making](https://docs-v3-preview.elastic.dev/elastic/docs-content/tree/main/deploy-manage/distributed-architecture/discovery-cluster-formation/modules-discovery-quorums)