[ MAC ] My backups halt in Sierra

I upgraded to a 27-inch iMac with a 1TB Fusion Drive, but every time it tries to run a Time Machine backup, the process stalls at the same point. I have even bought a new external hard drive, but it won’t complete the first backup to that either. Is Time Machine broken in Sierra?

Howard Oakley replies: Some users have reported problems backing up with Time Machine, but most of these issues can be fixed. If you can, archive the drive containing your old backups and switch to using the new one, starting afresh with it. Ensure that Sierra is fully up to date, and that there’s ample free space on the external drive to perform a full backup, as well as incremental backups thereafter. It’s also wise to check that any migration from your old Mac didn’t bring old or buggy software across to your new one, particularly extensions and enhancements. Turn off Time Machine, connect the new external drive, and restart in macOS Recovery. Using Disk Utility there, run First Aid on your Fusion Drive, then initialise the external drive to Mac OS Extended (Journaled) format. Restart your Mac as normal. In Time Machine’s preferences, click Options and add any folders you don’t want backed up to the exclusions. Re-enable Time Machine to back up to the new drive. Leave the iMac alone to back up, running no apps; overnight is ideal. If Time Machine sticks again, Sierra’s Console isn’t much help in diagnosing it. You could try to use Recovery to reinstall Sierra, erase the new back-up drive, and then try again.