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Came home to shut-down iMac (late 2015 running OS Big Sur 11.2.3). When I restarted, Time Machine told me I cannot back up to the Seagate 5 TB hard drive (installed in Oct 2020) that I had been using; it's now read-only.
I restarted; no change.
Screenshot of Seagate drive info attached. Suggestions? Many thanks.
Well, good and bad. That doesn't necessarily mean that you drive is failing; disk utility would tell you your drive is failing. Instead it's usually just something corrupt that cannot be fixed. I've had this happen a few times over the years and the drives still worked for years.
https://support.apple.com/guide/disk-utility/repair-a-storage-device-dskutl1040/mac
At this point, the best option is to reformat the drive and use it for a new time machine backup. I'd use one of the APFS formats.
https://support.apple.com/guide/mac-help/types-of-disks-you-can-use-with-time-machine-mh15139/mac.
Well, good and bad. That doesn't necessarily mean that you drive is failing; disk utility would tell you your drive is failing. Instead it's usually just something corrupt that cannot be fixed. I've had this happen a few times over the years and the drives still worked for years.
https://support.apple.com/guide/disk-utility/repair-a-storage-device-dskutl1040/mac
At this point, the best option is to reformat the drive and use it for a new time machine backup. I'd use one of the APFS formats.
https://support.apple.com/guide/mac-help/types-of-disks-you-can-use-with-time-machine-mh15139/mac.
The format shouldn't be an issue. This might help: https://support.apple.com/guide/mac-help/types-of-disks-you-can-use-with-time-machine-mh15139/mac.
But, maybe you have an issue with the drive? If you can, I'd use disk utility, first aid to check for errors on the drive.
Then, I'd probably reformat to one of the APFS formats. And select the disk.
You'll lose your older backups, but get the opportunity to wait (a while) for it to backup brand new.
FYI, when I upgraded my 2019 iMac to Big Sur, both my external drives remained HFS+ aka Mac OS Extended for a long time, till I started having issues in April with Time Machine perpetually preparing backups and not making a backup.
one of the suggestions was to reformat as APFS, which I did but only for one of the disks, so now I have one APFS Time Machine and one HFS+
and by the way, it did not help, and I still cannot get Time Machine to back up...
see: Time Machine fails to back up - perpetual… - Apple Community
Yes. Hold down the Option key and to to the ➙ System Information… menu item. In the sidebar check the section "Installations". It will list all installations, you can sort bye date) and get when you first upgraded to Big Sur.
I'm backed up now to the reformatted Seagate external drive. (Took 15 hours.) I read Muguy's links and proceeded accordingly.
This Seagate page is excellent: https://www.seagate.com/support/kb/how-to-format-your-drive-apfs-on-macos-big-sur-and-later/
I had a moment when I saw the Disk Utility box tell me it was formatting as Mac OS Extended (Journaled), but it quickly moved on to APFS.
I'm going to assume the original problem was caused by my update to Big Sur. Never would have thought of that, so thanks all for the troubleshooting and education.
Time Machine drives in Big Sur are formatted as APFS, not Mac OS Extended as they were in previous versions.
Are you saying you had been using this drive as it is now, in Big Sur already? This would be surprising to me. When I upgraded to Big Sur I reformatted my TM drive (I had other backups).
I am now officially way out of my depth. Thanks for the detailed instructions.
Here are shots of my most recent backups log (all to the same Seagate drive) and installations log.
Thanks for this idea. Bad news: Repair failed. Next?
Interesting... Can I query my Mac to find out when I upgraded to Big Sur?
I would imagine that case-sensitive would have been an issue as well.
It seems that Time Machine prefers Case Sensitive as that's what it formatted my rotational drive to (APFS Case Sensitive) when I reset it.
Suggestions for what to do next? Reformat the Seagate?
Thanks much, will report back.
Need help with Time Machine backups to Seagate 5TB external drive
