---
title: "Scale a Redis cluster"
sidebar_label: "Scale a cluster"
sidebar_position: 10
description: "How to change the configuration of Redis cluster nodes"
---

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# Scale a Redis cluster

A Redis Managed Database cluster can be [scaled](#resize-cluster). For example:

* increase RAM to improve cluster performance;
* change the fixed node configuration to another fixed one — the disk size and RAM must be larger than in the previous configuration, the number of vCPUs can be decreased or increased.

See the list of [node configurations](/managed-databases/redis/configurations.mdx).

[The configuration change process](#resize-principle) depends on whether there are replicas.

## How it works \{#resize-principle}

The configuration change process depends on whether there are replicas:

* if the cluster has no replicas — the master node will be shut down while changes are being applied, and the cluster will be temporarily unavailable for read and write operations;
* if the cluster has replicas — the cluster will be available for read and write operations while changes are being applied. Replicas will be shut down one by one, and the configuration of each will be changed. Then the master node will switch to one of the replicas, and the configuration of the previous master node will be changed.

The time taken to change the configuration depends on the volume of data in the cluster.

## Scale a cluster \{#resize-cluster}

1. Scale the cluster when user activity is at its lowest.
2. To avoid shutting down the master node in a cluster without replicas, [add a replica](/managed-databases/redis/cluster-fault-tolerance.mdx#change-number-of-replicas). You can remove the replica after scaling.
3. In the [Dashboard](https://my.selectel.ru/vpc/default/dbaas/), on the top menu, click **Products** and select **Managed Databases**.
4. Open the **Active** tab.
5. Open the cluster page → **Settings** tab.
6. Click **Change configuration**.
7. Select another [fixed configuration](/managed-databases/redis/configurations.mdx). You can only select configuration with higher RAM and disk capacity. The number of vCPUs can be decreased or increased.
8. Optional: [increase the number of replicas](/managed-databases/redis/cluster-fault-tolerance.mdx) in the cluster.
9. Click **Save**.
10. After scaling, [clear the DNS cache](#clear-dns-cash).
11. Check if the cluster has been scaled correctly.

## Clear DNS cache \{#clear-dns-cash}

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  <TabItem value="ubuntudebian" default>
    <TabItemLabel>
      Ubuntu/Debian
    </TabItemLabel>

    1. Open the CLI.
    2. Clear the DNS cache:

       ```bash
       sudo systemctl restart systemd-resolved
       ```
  </TabItem>

  <TabItem value="centos">
    <TabItemLabel>
      CentOS
    </TabItemLabel>

    1. Open the CLI.
    2. Clear the DNS cache:

       ```bash
       sudo dscacheutil -flushcache
       ```
  </TabItem>

  <TabItem value="macos">
    <TabItemLabel>
      macOS
    </TabItemLabel>

    1. Open the CLI.
    2. Clear the DNS cache:

       ```bash
       sudo systemctl restart network
       ```
  </TabItem>

  <TabItem value="windows">
    <TabItemLabel>
      Windows
    </TabItemLabel>

    1. Open the CLI as an administrator.
    2. Clear the DNS cache:

       ```bash
       ipconfig /flushdns
       ```
  </TabItem>
</Tabs>

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