How files stored only in iCloud are backed up

Updated

With Optimize Mac Storage turned on, macOS keeps many files only in iCloud and removes their contents from your Mac. CloudBak calls these cloud-only files. To copy one to your backup, CloudBak has to download it first.

What happens to each cloud-only file

  1. Looking through iCloud Drive for changes doesn't download anything.
  2. Cloud-only files are downloaded a few at a time, within the space you've set aside for them.
  3. Each one is copied to your backup folder and checked.
  4. It's then returned to iCloud, which frees the space on your Mac again. Activity shows this as Freeing Space.

Only files the backup downloaded are returned to iCloud. Files that were already on your Mac stay on your Mac.

Backing up never changes your files in iCloud Drive. It only reads them.

How much space it takes

Two settings in Settings › Storage decide how much room downloads may take at once. See Disk space on your Mac during a backup.

The iCloud Drive card on the Overview screen shows how much of your iCloud Drive is On this Mac and how much is Cloud-only.

Documents that are kept as one item

A document such as a Pages file or a GarageBand project looks like one file in Finder but holds many inside. CloudBak downloads and backs it up whole.

A document CloudBak hasn't backed up before, and that's only in iCloud, can't be measured until it's downloaded. So it comes down on its own, with nothing else downloading beside it.

If you stop or pause

  • Stop: anything downloaded for the backup is returned to iCloud.
  • Pause: files already downloaded stay on your Mac until you resume or stop the backup.

If a download fails or takes too long

A file that can't be downloaded, or whose download takes too long, is listed in Issues as Couldn't Read From iCloud. It isn't changed, and it's tried again in the next backup. See What the issues in the Issues list mean.

How CloudBak tells which files are cloud-only

In Settings › iCloud Drive, under Finding Cloud-Only Files, you can choose:

  • Read the flag on this Mac: the standard setting, and much faster.
  • Ask iCloud about every file: choose this only if CloudBak seems to be wrong about which files are stored only in iCloud.

The choice applies to the next scan of iCloud Drive.