Snapshot

A snapshot freezes the state of all disks of a VM at a moment in time (often including RAM — then called a live snapshot). Implementation relies on copy-on-write features of the underlying storage layer (ZFS, LVM, Ceph RBD, Btrfs): instead of duplicating data, the system only records changes after the snapshot point — creation takes seconds, not minutes. Snapshots do not replace backups: they sit on the same storage and protect neither against storage failure nor against provider insolvency. Useful as a safety net before risky updates, migrations or configuration changes — restore with one click takes you back to square one. Cloud providers like Hetzner Cloud price snapshots at around €0.01/GB/month.