Backups

ClickHouse® is currently at the design stage of creating some universal backup solution. Some custom backup strategies are:

1. Each shard is backed up separately.
2. FREEZE the table/partition. For more information, see Alter Freeze Partition .
   1. This creates hard links in shadow subdirectory.
3. rsync that directory to a backup location, then remove that subfolder from shadow.
   1. Cloud users are recommended to use Rclone .
4. Always add the full contents of the metadata subfolder that contains the current DB schema and ClickHouse configs to your backup.
5. For a second replica, it’s enough to copy metadata and configuration.
6. Data in ClickHouse is already compressed with lz4, backup can be compressed bit better, but avoid using cpu-heavy compression algorithms like gzip, use something like zstd instead.

The tool automating that process: Altinity Backup for ClickHouse .