Intermittent Time Machine backup failures (macOS 12.5 Monterery)

MJ wrote:

On this Mac mini (M1, 2020) Time Machine backups intermittently fail. I estimate the failure rate is about 40% ... 4 out of 10 attempted backups fail.

When I search the logs for "backupd" the most telling entry is:

com.apple.message.signature: BACKUP_FAILED_COPY_STAGE

I really mean intermittent; some times the back works fine. I have two external Time Machine drives (different models, different vendors) and they both exhibit this intermittent failure problem.

Manual backups (via "Back Up to ... now") also fail intermittently.

Time Machine worked flawlessly until about the time I upgraded to Monterey (from Big Sur). I am not saying there is cause and effect here but the upgrade is by far the most dramatic change to my system recently.

All drive will fail over time, not if but when; some drive fail brand new out of the box.

"Time Machine has completed a new backup for you, or get a message saying it can't create the backup,"

or “failed to complete the backup, ” or “Preparing backup”

This message reappears most likely the TimeMachine disk is operating in a state of failure and will continue to fail with increasing frequency—in this case replace the drive and compare your results.

If you value your user data

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

More than one device, more than one backup methodology.

All new drives should be erase/formatted/initialized when new...

—esepecially those drives that charge more and say something similar to "Mac ready"... these always include proprietary software that you have no control, or need updates as you move forward.

Erase and reformat a storage device in Disk Utility on Mac

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Learn more about backup disks that you can use with Time Machine —Backup disks you can use with Time Machine - Apple Support

Since you appear to be familiar with accessing your Mac's logs, I suggest that you try using the free Mints tool from The Eclectic Light Company. I use it to review the Time Machine backup process to see where it fails to help with troubleshooting.

Ref:

• Time Machine: 2 What it writes in the log - The Eclectic Light Company
• Time Machine 16: Reading a normal backup in Catalina using Mints - The Eclectic Light Company << Still applies to Monterey

Again, I would suggest that you give Mints a try. It should provide you with a much clearer view of your Mac's processes during an actual backup ... or look at past backups that are in the logs. The second link I provided you would be used as a baseline of what a "normal" backup writes to the logs.

I’m not sure where it is stored, but maybe exclude the OneDrive storage location to see if that is the issue.

Ok, got it. Thanks for giving it a try. I'm sorry it didn't help in this case.