PBS splits data into 4 MB chunks, computes SHA-256 hashes, and stores each unique chunk once. 30 daily backups of a 50 GB VM take only ~80 GB instead of 1500 GB.
proxmox-backup-manager datastore show backup-store
# Dedup Factor: 5.8x
proxmox-backup-client key create /etc/pve/priv/backup.key
proxmox-backup-client key paperkey /etc/pve/priv/backup.key
Store the encryption key in 3 places: on PBS, in a password manager, and physically (print the QR paperkey). Losing the key means losing all encrypted backups.