If you frequently use virtual machine container files (e.g. with Parallels, VMWare, VirtualBox, etc.), you may find that CCC's SafetyNet folder tends to get very large, very quickly, or that snapshots on the destination consume space very quickly. Every time you open your virtual machine, the monolithic virtual machine container file is modified, and CCC will require that it gets backed up during the next backup task. If the SafetyNet is on, CCC will move the older version of the VM container file into the SafetyNet folder (or it will be retained by a snapshot on the destination). If you run your backup tasks on a daily basis and use your virtual memory container file every day, these large VM container files will quickly consume all of the free space on your backup volume.

The best way to avoid bloat on your backup volume is to create a new, dedicated backup volume for the VM container. Here's how to set things up:

  1. Open Disk Utility
  2. Select your current APFS-formatted destination volume in the sidebar
  3. Click the "+" button in the toolbar; name the new volume something like "Parallels Backup"
  4. In the Finder, delete the Parallels VM folder from your primary backup volume
  5. Open CCC
  6. Create a new task and name it something like Everything except Parallels
  7. Choose your startup disk from CCC's Source selector
  8. Click the Task Filter button at the bottom of the window
  9. In the file list in the Task Filter window, navigate to the location where your Parallels VM is saved (e.g. Users > yourname > Documents > Parallels) and uncheck the box next to the folder that contains your virtual machine container. You could exclude the container file itself, but choosing the parent folder gives you more flexibility in renaming the VM container, should you want to (e.g. Windows XP > Windows 7).
  10. Choose your backup volume from the Destination selector
  11. Configure the task to run Daily and Save the changes
  12. Create a new task and name it something like Parallels Backup
  13. Choose Choose a folder... from the Source selector and select your Parallels folder as the source (e.g. the same folder that you excluded previously). By selecting this folder directly, you're explicitly limiting this task's scope to this folder.
  14. Click on the Destination selector and select the "Parallels Backup" volume as the destination
  15. Click on the Destination selector and choose SafetyNet Off from the SafetyNet menu
  16. Schedule this task, then save the changes
  17. Click on the Destination selector and choose "Manage snapshots on 'Parallels Backup'"
  18. Disable snapshot support on the "Parallels Backup" volume

Additionally, you can configure the first task to run that second task as a postflight action in Advanced Settings.