Why it matters

Data loss from bad Cassandra backup practices is a common enterprise incident. Getting backups right is basic operational hygiene.

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The architecture

Snapshot: nodetool snapshot creates hard links to current SSTables in snapshots/ directory. Instant, uses no extra space initially.

Incremental backup: on flush, new SSTable hard-linked to backups/ directory. Enables PITR-style recovery.

Backup workflowSnapshothard links to SSTablesIncremental backupon-flush copiesOff-cluster copyS3 / other DCRestore: copy files back to data dir, restart node; complex to restore consistent snapshot across cluster
Backup + restore flow.
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How it works end to end

Off-cluster storage: after snapshot, copy files to S3 or another DC. rsync or dedicated tools like Cassandra Backup Solutions.

Restore per-node: copy files to data directory, then use nodetool refresh or restart.

Cluster-wide consistent restore is hard: snapshots aren't taken at the same instant across nodes. Coordinate via out-of-band tools or accept eventual consistency after restore.