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Scale a ClickHouse® cluster

In a ClickHouse® cloud database cluster, you can add or remove shards. To add a shard to a cluster consisting of one shard with one node, you must first add ClickHouse® Keeper. The ClickHouse® Keeper node group is mandatory for all cluster configurations except the single-node one.

You can also scale node groups — shards and ClickHouse® Keeper. For example:

  • change the configuration within lines with fixed configurations — you can only select a configuration with a disk 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. It is not possible to change a line with a local volume to a line with a network volume and vice versa.

Add shard

You can add only one shard at a time. There can be no more than ten shards in a cluster.

  1. If the cluster consists of only one shard with one node, add ClickHouse® Keeper.

  2. In the Dashboard, 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.

  8. If you selected a line with custom configurations, select the disk type and specify the number of vCPUs, RAM size, and disk size.

  9. If you selected a line with fixed configurations, select a configuration.

  10. Specify the number of nodes in the shard.

  11. Optional: to make shard nodes accessible from the internet, select the Enable public access checkbox. For each shard node, a separate public IP address will be assigned.

    If the cluster subnet does not meet the requirements, public access cannot be enabled. You can prepare a private subnet and assign a public IP address after adding the shard.

  12. Optional: specify the shard weight. Values from 0 to 65535 are available.

  13. Click Save.

Add ClickHouse® Keeper

For your information

The ClickHouse® Keeper node group 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 section of the ClickHouse® documentation.

  1. In the Dashboard, 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 name.

  6. Select a configuration line.

  7. If you selected a line with custom configurations, select the disk type and specify the number of vCPUs, RAM size, and disk size.

  8. If you selected a line with fixed configurations, select a configuration.

  9. Click Save.

Delete shard

carefully

Deleting a 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, 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

warning

Active connections to the nodes will be interrupted during the node group scaling process.

  1. In the Dashboard, 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 the node group. You can:

    • change the configuration within lines with fixed configurations — you can only select a configuration with a disk 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. It is not possible to change a line with a local volume to a line with a network volume and vice versa.

  7. Click Save.

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