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Transfer data between storage devices in Aiven for ClickHouse®'s tiered storage

Moving data from SSD to object storage allows you to size down your SSD by selecting a service plan with less SSD capacity. You can move the data back to your SSD anytime.

You can transfer data between storage devices in Aiven for ClickHouse® using SQL statements against your tables directly.

Prerequisites​

  • At least one Aiven for ClickHouse service
  • Command line tool (ClickHouse client) installed

Transfer data from SSD to object storage​

If you enable the tiered storage feature on your table, by default your data is moved from SSD to object storage as soon as the SSD reaches 80% of its capacity.

  1. Connect to your Aiven for ClickHouse service using, for example, the ClickHouse client.

  2. Run the following query:

    ALTER TABLE database-name.tablename MODIFY SETTING storage_policy = 'tiered'

Now, with the tiered storage feature enabled, your data is moved from SSD to object storage when the SSD reaches 80% of its capacity.

note

You can also configure your tiered storage so that data is moved to object storage at a specific time.

Transfer data from object storage to SSD​

Use the MOVE PARTITION|PART statement to transfer data to your SSD.

  1. Connect to your Aiven for ClickHouse service using, for example, the ClickHouse client.

  2. Select a database for operations you intend to perform.

    USE database-name

  3. Run the following query:

    ALTER TABLE table_name MOVE PARTITION partition_expr TO VOLUME 'default'

Your data has been moved to the SSD.

What's next​