Product: 
ccc6

By default, CCC attempts to be fairly conservative about deleting content from the destination. In most cases CCC will effectively make enough room on the destination by deleting older, out of date content, but depending on the settings you're using, that may not be possible or practical. Here are some things you can do to get past a "destination is full" error.

Use default SafetyNet settings

By default, CCC tasks have SafetyNet enabled, and CCC starts with a SafetyNet pruning limit that will establish 25GB of free space on the destination at the beginning of each backup task. CCC will increase that limit automatically as necessary if the task finds more than 25GB of files to update. If you have customized CCC's SafetyNet setting or the SafetyNet pruning settings, try setting them back to the default values:

  1. Select your task in CCC's main application window.
  2. Click on the Destination selector and choose SafetyNet On from the SafetyNet submenu.
  3. Click the Advanced Settings button at the bottom of the window.
  4. Set the Prune the SafetyNet setting to When free space is less than.
  5. Set the pruning limit to 25 (or a larger value).
  6. Check the Auto adjust checkbox so CCC can manage this value for you automatically.
  7. Click the Done button, then run the backup task again.

If snapshots are enabled on your destination volume, you won't configure per-task pruning settings, rather you will adjust the SafetyNet retention settings in the Snapshot Retention Policy for the volume. Follow the steps above, but click on the Snapshot Pruning Settings button at step 3 to find those settings.

Disable the SafetyNet feature, and disable "Protect root-level items on the destination"

If your source data set is very close to the capacity of the destination volume, then it may not be practical to use the SafetyNet feature.

  1. Select your task in CCC's main application window.
  2. Click on the Destination selector and choose SafetyNet Off from the SafetyNet sub menu.
  3. If prompted, choose the Remove SafetyNet option to have the existing SafetyNet folder deleted from the destination immediately.
  4. Click on the Destination selector again and select the SafetyNet submenu. If the Protect root-level items on the destination menu item is checked, select that item to disable that setting.
  5. Save and run the backup task.

When you disable the SafetyNet, all files on the destination are subject to permanent removal – any file that does not exist on the source will be deleted. If you have any doubt about whether content on the destination may be removed, click the Preview button in CCC's toolbar to preview the changes before running the task.

Use a larger destination

Ideally, your destination volume will have about twice the capacity as space consumed on the source. That allows ample room for data growth and snapshot retention. If your source data set is larger than, or very close to the capacity of the destination, then it may not be possible to perform safe updates to files on the destination, even with the SafetyNet feature disabled.

Choosing a backup drive: Devices that we recommend

My destination is larger than the source data set, how could CCC be claiming that the destination is full?

We see this occasionally in cases where the source is an APFS volume, and has "cloned" files on it. For example, if you duplicated a Photos Library, the Finder would create the copy pretty quickly, but the second copy wouldn't consume any additional disk space. Magic! It's a feature of Apple's new APFS filesystem, but those space savings can't be preserved when you copy stuff to another disk – the two copies of the Photos library (for example) would consume twice the space on the backup disk. We demonstrate the issue in this video: Finder does not accurately represent the true disk usage of your files.

If you happen to remember duplicating a really large file recently, then you could exclude the duplicate from your backup task (or delete it if it's unnecessary). Alternatively, you should back up to a larger destination device.

Related Documentation