# Transfer data between storage devices in Managed ClickHouse®'s tiered storage


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

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

## Prerequisites

-   At least one Managed ClickHouse service
-   Command line tool
    ([ClickHouse client](/product/dbaas/service-specific/clickhouse/how-to/connect-with-clickhouse-cli/))
    installed

## Transfer data from network-attached block storage to object storage

**Automatic data transfer**

If you
[enable](/product/dbaas/service-specific/clickhouse/how-to/enable-tiered-storage/) the tiered storage feature
on your table, by default your data is moved from network-attached block storage to object
storage as soon as it reaches 80% of its capacity.

1.  [Connect to your Managed ClickHouse service](/product/dbaas/service-specific/clickhouse/how-to/list-connect-to-service/)
    using, for example, the ClickHouse client.

1.  Run the following query:

    ```sql
    ALTER TABLE database_name.table_name MODIFY SETTING storage_policy = 'tiered'
    ```

Now, with the tiered storage feature
[enabled](/product/dbaas/service-specific/clickhouse/how-to/enable-tiered-storage/), your data is moved from
network-attached block storage to object storage when it reaches 80% of its capacity. You can
[adjust that threshold](/product/dbaas/service-specific/clickhouse/how-to/configure-tiered-storage/#size-based-threshold)
at the service level.

> [!NOTE]
> You can also
> [configure your tiered storage](/product/dbaas/service-specific/clickhouse/how-to/configure-tiered-storage/)
> so that data is moved to object storage at a specific time.

**Manual data transfer**

To move data manually from network-attached block storage to object storage, first list the
partitions of your table:

```sql
SELECT partition, formatReadableSize(sum(data_compressed_bytes)) AS size
FROM system.parts
WHERE database = 'default' AND table = 'trips' AND active
GROUP BY partition
ORDER BY partition
```

Then move a partition by its value. On the quick-start `trips` table, partitioned by
`toYYYYMM(pickup_date)`, a partition value looks like `201507`:

```sql
ALTER TABLE default.trips MOVE PARTITION 201507 TO VOLUME 'remote'
```

To configure data retention thresholds to automatically move data from network-attached block
storage to object storage, see
[Configure data retention thresholds in Managed ClickHouse®'s tiered storage](/product/dbaas/service-specific/clickhouse/how-to/configure-tiered-storage/).

## Transfer data from object storage to network-attached block storage

Use the
[MOVE PARTITION\|PART](https://clickhouse.com/docs/reference/statements/alter/partition#move-partitionpart)
statement to transfer data to network-attached block storage.

1.  [Connect to your Managed ClickHouse service](/product/dbaas/service-specific/clickhouse/how-to/list-connect-to-service/)
    using, for example, the ClickHouse client.

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

    ```sql
    USE database_name
    ```

1.  Run the following query:

    ```sql
    ALTER TABLE table_name MOVE PARTITION partition_expr TO VOLUME 'default'
    ```

Your data has been moved to network-attached block storage.

## What's next

-   [Check data distribution between network-attached block storage and object storage](/product/dbaas/service-specific/clickhouse/how-to/check-data-tiered-storage/)
-   [Configure data retention thresholds for tiered storage](/product/dbaas/service-specific/clickhouse/how-to/configure-tiered-storage/)

-   [About tiered storage in Managed ClickHouse](/product/dbaas/service-specific/clickhouse/overview/clickhouse-tiered-storage/)
-   [Enable tiered storage in Managed ClickHouse](/product/dbaas/service-specific/clickhouse/how-to/enable-tiered-storage/)