Time Machine not working on WD "My Book" after updating to Big Sur 11.5.1

I've been playing with this and think I know what the problem is. I think my external 4 TB WD "My Book" drive is bad. It won't pass Disk Utility and stops before the First Aid program can finish. My MBPro works fine with it's 2 TB drive, and it passes First Aid just fine. I can see the files on the backup folder and hope that if I get a new drive and then copy the files to the new drive that it will work. I've learned a lot today. I think the WD 4 TB drive is defective and so Time Machine can't access it. I can see the backup files with Finder. Think I'll buy a new disk drive tomorrow and see if I can copy the backup files to it. Would be best to get an SDD drive, but they are fairly costly. I don't think it has anything to do with Big Sur. Thanks all for the comments during the day.

Thank you, Jefffreythe frog!

Great information and this is what is causing my problem. the 4TB WC external drive is formatted Mac OS Extended and not APFS. The 1 TB internal Fusion Drive is formatted to APFS and was modified on 1/1/2020. Not sure if the macOS was updated then as this was purchased new in 2015 and I don't know which format the drive had back then. I suspect a macOS update caused to be updated from Mac OS Extended ?? Or, was the fusion drive originally APFS?

I also have a MacBook Pro purchased in 12/2017. It's 500 GB SSD is formatted APFS. It is currently running macOS Big Sur 11.4 and uses a WD My Passport for MAC 2TB external drive for Time Machine. The external drive is formatted Mac OS Extended. Time Machine is working just fine on this drive. Did Big Sur 11.5 require the APFS format on external drives for Time Machine to work? That is my assumption, based on what I see in the MBPro.

This is confusing. I don't want to update the MBPro to 11.5 until I figure this out.

Why didn't Apple warn us that this would be a problem with Big SUR? Looks like it is a big problem for a lot of people. I really don't want to lose seven years of history on my iMac. That is the reason I rely on Time Machine as it has up to this point been very reliable. If I buy another new external drive and format it AFPS, is there a way to copy these backup files from the 4 TB disk to the newly formatted backup disk? Sounds kind of scary to try.

So did the external disk format requirement come in with 11.5?

Any way to transfer this data to another external disk formatted with APFS? Same question as above. Could I do it on my MBPro since is can still read a Mac Extended formatted disk. I'm more concerned with the data on the iMac than the MBPro as the MBPro has a subset of the data on the iMac..

Wow, this isn't like Apple to cause such a difficult problem with an upgrade.

Again thanks for your help. any other suggestions?

tbirdvet

Interested in your comment. I formatted both of these external drives using Disk Utility and it formatted them to HFS in 2020. Your comment makes me wonder if I need to reformat the external drive and lose all my historical data. I'm confused as to why my iMac running MacOS 11.5.1 had this problem, but my MBPro running MacOS 11.4 doesn't have the problem and time machine is working fine there. Both drives are formatted HFS. Could there be another explanation for the problem with time machine on the iMac?

Not seeing much on this from Apple.

Thanks for your reply.

veehbj

Thanks for the clarification. I can buy a new external disk and reformat it. That will probably solve this problem. I can keep the 4 TB external with my Time Machine files and access the files with Finder manually if I need to find a historical file. That works. Really don't need a 4 TB file back up disk.

So looks like the HFS+ file system is accessible from Big Sur 11.51, but time machine won't work. I'm also concerned that Disk Utility won't run First Aid on the disk. Both computer's external WC drives fail in First Aid under Big Sur. Is there a problem with Disk Utility analyzing or repairing a HFS+ file system? Or, do I have two defective WC external drives?

Also, why does Time Machine run on my MBPro running Big Sur 11.4 ? Has it to do with the Big Sur 11.5 update? I am still at 11.4 on the MBPro.

I ran Disk Utility on the 2 TB external drive on the MBPro and it also failed. But, it is working with Time Machine under Big Sur 11.4 just fine.

I also saw something that said that the APFS does not support Fusion Drives. The iMac has a 1 TB Fusion drive. This is all very confusing. It seems to be working just fine, except for Time Machine.

Lots of questions and I appreciate your experience and willingness to help me understand this.

Thanks again for your help with this.

Did the requirement for APFS come in with the upgrade to Big Sur 11.5? See my comments below. This is confusing.

veehbj