{ ... }:
{
  systemd.tmpfiles.rules = [
    "d /mnt/storage/private.bak 0755 root root"
    "d /mnt/storage/public.bak 0755 root root"
  ];

  services.btrbk.instances = {
    mnt-storage-private = {
      onCalendar = "hourly";
      settings.volume."/mnt/storage" = {
        subvolume = "private";
        snapshot_dir = "private.bak";
        snapshot_preserve_min = "latest";
        snapshot_preserve = "48h 14d 4w 6m";
      };
    };

    mnt-storage-public = {
      onCalendar = "hourly";
      settings.volume."/mnt/storage" = {
        subvolume = "public";
        snapshot_dir = "public.bak";
        snapshot_preserve_min = "latest";
        snapshot_preserve = "48h 14d 4w 6m";
      };
    };
  };
}