Mac software quick-fire questions
How do I fix errors when backing up iCloud Drive?
Work around Time Machine errors like this by adding your iCloud Drive to its exclusion list, via the Options… button in the Time Machine pane.
How do I use an APFS SSD or Flash with Sierra?
If you’ve formatted removable storage using this new file system, you can’t use it with Sierra or earlier: share it from your High Sierra system instead.