Content-defined dedup
Unlike fixed-block dedup, PBS uses a rolling Buzhash to find natural chunk boundaries. A 1-byte insert into a 100 GB file does not invalidate the entire backup. Real-world dedup ratios: 5:1 to 12:1.
Incremental forever
Only changed chunks are transferred and stored. A 1 TB VM with 1% daily change writes ~10 GB per backup, not 1 TB.
Client-side encryption
AES-256-GCM. With client-side mode, the PBS server never sees plaintext. Critical for FRA15 hosted backups where compliance demands encryption boundary at the customer.
Practice numbers: Typical ratios from our customer base — 7 TB raw data → 1 TB stored. 1 TB VM with daily backup over 30 days → ~40 GB total storage. Restore times: P50 ≈ minutes, P99 dependent on chunk locality.
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