This is why Proxmox Backup Server has scheduled "verify" tasks which look at the sha256 of every stored hunk to make sure it hasn't rotted on disk. (If it has,

This is why Proxmox Backup Server has scheduled "verify" tasks which look at the sha256 of every stored hunk to make sure it hasn't rotted on disk. (If it has, it makes sure to re-acquire that data on the next backup - hopefully it's still available!)