Data Restore

Restoring data from backups is crucial for ensuring data availability, especially in scenarios such as keyspace deletion, launching a new cluster from backup data, or replacing a node. The restoration process typically involves utilizing snapshots and incremental backup files.

There are two primary methods for restoring data from backups:

Using nodetool refresh

The nodetool refresh command enables the loading of newly placed SSTables onto the system without requiring a restart. This method is useful when a new node replaces an unrecoverable node. To restore data from a snapshot using this method, follow these steps:

• Create the necessary schema if it doesn't already exist.

• Truncate the table if needed.

• Locate the snapshot folder (e.g., /var/lib/keyspace_name/table_name-UUID/snapshots/snapshot_name) and copy the snapshot SSTable directory to the /var/lib/keyspace/table_name-UUID directory.

• Execute the nodetool refresh command.

Using sstableloader:

The sstableloader is a tool for loading a set of SSTable files into a Cassandra cluster. It offers options for loading external data, existing SSTables, and restoring snapshots. To restore data using sstableloader, follow these steps:

• Create the required schema if it's not already present.

• Truncate the table if necessary.

• Bring the backup data to a node from a storage service like AWS S3, Google Cloud, or MS Azure (e.g., download the backup data to /home/data).

• Run the following command:

  sstableloader -d <ip> /home/data

Note: Replace <ip> with the appropriate IP address.

By following these methods, data can be effectively restored from backups, ensuring data availability and recovery in various scenarios.