This seems like a problem that needs some press coverage to get some attention within Apple to solve.
Long story short: After finding this thread, I tried reformatting my Western Digital external drive (used exclusively for Time Machine) as Mac OS Extended Journaled Case-Sensitive. Time Machine was able to complete its first backup. Success! (I hope).
The history: I have an iMac 27” (2015) with two external drives - one for media, one for Time Machine. six months ago (running High Sierra), my iMac would randomly lock up with the spinning beach ball cursor whenever Time Machine would start a backup.
I did a complete wipe-and-reinstall High Sierra from recovery. I also wiped the Time Machine drive. I couldn’t complete the first Time Machine backup without beach-balling. I thought the Time Machine drive might have been failing. I decided to replace my media drive with a higher capacity drive and repurpose the media drive for Time Machine.
Bought a new Western Digital drive and transferred the contents of my media drive. My first Time Machine backup worked. Problem solved, I thought.
A couple weeks ago, the problem resurfaced. Whenever Time Machine attempted a backup, the iMac would beach-ball. I figured it was drive failure again — fortunately, the drive was under warranty. RMA’d with Western Digital and a few days later I had a replacement. Formatted it with Disk Utility and started Time Machine.
A few hours in, the first backup failed. After that, whenever Time Machine started a backup the iMac would lock up. Even opening a Finder window from a fresh boot would cause the beachball.
Looking at the various forums and just getting desperate, over the next several days I:
- Booted into recovery and ran Disk First Aid on all drives
- NVRAM reset, SMC reset
- Wiped and reinstalled macOS Mojave
- Wiped my media drive and did a secure erase to try to identify/avoid bad blocks (that alone took 18 hours)
- Copied the contents of my media drive to my (now initialized) Time Machine drive and vice versa (no errors)
- Used an old Mac running pre-High Sierra to initialize my Time Machine drive (I don’t remember where I read this suggestion)
- Turned off (or excluded) the Time Machine drive from Spotlight
- Confirmed I was not running AppCleaner or anything else other than the bare Mojave install
- Opened a support case with Apple - spent an hour trying various troubleshooting steps to come to the conclusion that Western Digital drives are not compatible with macOS and that I should take it up with them
- Went through my media drive and found that I had previously copied an old Library folder from years ago— I threw it away in case there were any files in there that may have been causing a problem
- Reformatted the Time Machine drive as Mac OS Extended (Journaled, Case Sensitive)
One of the last two (or both) appears to have solved the problem. Time Machine was able to complete its first backup. I can open a Finder window without locking up. So far, Time Machine backups aren’t locking up the iMac.
While I’m happy that my problem appears to have been solved by one of the workarounds, it still mean the root cause needs to be solved. I’ve also reported this using Apple’s feedback page, but given how many threads I’ve found with the same issue (going back to High Sierra) and with two bug-fix releases of Mojave that haven’t fixed this, is there any other way to get some visibility on this?
I wonder how many hard drives have been neeedlessly discarded (and how much money has been spent on new drives) because people assumed it was hard drive failure?