---
title: "Scale a ClickHouse® cluster"
sidebar_label: "Scale cluster"
sidebar_position: 13
description: "How to change the configuration of node groups in a ClickHouse® cluster"
---
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# Scale a ClickHouse® cluster
You can [add](#add-shard) or [delete shards](#delete-shard) in a ClickHouse® Managed Databases cluster. To add a [shard](/managed-databases/clickhouse/about-node-groups.mdx#shard) to a cluster consisting of a single shard with one node, you must first [add ClickHouse® Keeper](#add-clickhouse-keeper). [The ClickHouse® Keeper node group](/managed-databases/clickhouse/about-node-groups.mdx#clickhouse-keeper) is mandatory for all cluster configurations except the single-node one.
You can also [scale node groups](#resize-node-group) — shards and ClickHouse® Keeper. For example:
* change the [configuration](/managed-databases/clickhouse/configurations.mdx) within [lines](/managed-databases/clickhouse/configurations.mdx) with fixed configurations — you can only select a configuration with a [disk](/managed-databases/clickhouse/volumes.mdx) size larger than the current one;
* increase the number of vCPUs, RAM, and disk size in a line with custom configurations;
* change the configuration line to another one with the same disk type but a larger disk size. You cannot change a line with a local disk to a line with a network volume, or vice versa.
## Add shard \{#add-shard}
You can add only one [shard](/managed-databases/clickhouse/about-node-groups.mdx#shard) at a time. The cluster can have no more than ten shards.
1. If the cluster consists of only one shard with one node, [add ClickHouse® Keeper](#add-clickhouse-keeper).
2. In the [Dashboard](https://my.selectel.ru/vpc/default/dbaas/), on the top menu click **Products** and select **Managed Databases**.
3. Open the **Active** tab.
4. Open the database cluster page → **Settings** tab.
5. In the **Cluster** block, click **Add shard**.
6. Optional: change the shard name.
7. Select a [configuration line](/managed-databases/clickhouse/configurations.mdx).
8. If you selected a line with custom configurations, select the [disk](/managed-databases/clickhouse/volumes.mdx) type and specify the number of vCPUs, RAM size, and disk size.
9. If you selected a line with fixed configurations, select a [configuration](/managed-databases/clickhouse/configurations.mdx).
10. Specify the number of nodes in the shard.
11. Optional: to make the shard nodes accessible from the internet, select the **Enable public access** checkbox. A separate [public IP address](/managed-databases/clickhouse/public-ip.mdx) will be assigned to each shard node.
If the cluster subnet does not meet the [requirements](/managed-databases/clickhouse/public-ip.mdx#requirements), enabling public access is not available. You can [prepare a private subnet](/managed-databases/clickhouse/public-ip.mdx#configure-subnet) and [connect a public IP address](/managed-databases/clickhouse/public-ip.mdx#assign-public-ip-in-existing-cluster) after adding the shard.
12. Optional: specify the [shard weight](/managed-databases/clickhouse/about-node-groups.mdx#shard-weight). Values from 0 to 65 535 are available.
13. Click **Save**.
## Add ClickHouse® Keeper \{#add-clickhouse-keeper}
:::info
[The ClickHouse® Keeper node group](/managed-databases/clickhouse/about-node-groups.mdx#clickhouse-keeper) cannot be removed from the cluster after it has been added.
:::
When adding ClickHouse® Keeper, MergeTree tables are automatically converted to replicated tables (for example, to ReplicatedMergeTree). Learn more about replicated tables in the [Replicated\* table engines](https://clickhouse.com/docs/engines/table-engines/mergetree-family/replication) section of the ClickHouse® documentation.
1. In the [Dashboard](https://my.selectel.ru/vpc/default/dbaas/), on the top menu click **Products** and select **Managed Databases**.
2. Open the **Active** tab.
3. Open the database cluster page → **Settings** tab.
4. In the **Cluster** block, click **Add ClickHouse Keeper**.
5. Optional: change the [node group](/managed-databases/clickhouse/about-node-groups.mdx) name.
6. Select a [configuration line](/managed-databases/clickhouse/configurations.mdx).
7. If you selected a line with custom configurations, select the [disk](/managed-databases/clickhouse/volumes.mdx) type and specify the number of vCPUs, RAM size, and disk size.
8. If you selected a line with fixed configurations, select a [configuration](/managed-databases/clickhouse/configurations.mdx).
9. Click **Save**.
## Delete shard \{#delete-shard}
:::danger
Deleting a [shard](/managed-databases/clickhouse/about-node-groups.mdx#shard) will remove all data located on that shard.
:::
You can delete a shard from the cluster if it is not the only shard.
1. In the [Dashboard](https://my.selectel.ru/vpc/default/dbaas/), on the top menu click **Products** and select **Managed Databases**.
2. Open the **Active** tab.
3. Open the cluster page → **Settings** tab.
4. In the shard menu, select **Delete**.
5. Enter the shard name to confirm.
6. Click **Delete**.
## Scale node group \{#resize-node-group}
:::warning
Active connections to the nodes will be interrupted during the node group scaling process.
:::
1. In the [Dashboard](https://my.selectel.ru/vpc/default/dbaas/), on the top menu, click **Products** and select **Managed Databases**.
2. Open the **Active** tab.
3. Open the database cluster page → **Settings** tab.
4. In the node group menu, select **Change configuration**.
5. Optional: change the node group name.
6. Scale a node group. You can:
* change the [configuration](/managed-databases/clickhouse/configurations.mdx) within [tiers](/managed-databases/clickhouse/configurations.mdx) with fixed configurations — you can select a configuration only with a disk size larger than the current one;
* increase the number of vCPU, RAM, and [disk](/managed-databases/clickhouse/volumes.mdx) size in a [tier](/managed-databases/clickhouse/configurations.mdx) with custom configurations;
* change the configuration line to another one with the same disk type but a larger disk size. You cannot change a line with a local disk to a line with a network volume, or vice versa.
7. Click **Save**.
ClickHouse® is a registered trademark of ClickHouse, Inc. https://clickhouse.com.