External Hard Drive Missing After Big Sur Download

I was able to recover mine - here's how I did it. I'm going to write out my troubleshooting process as I'm not sure what 100% fixed it.

As I read through this discussion, I was dealing with identical scenario's... my Seagate 4TB external HD, on my Macbook Pro (late-2015) running on Big Sur, wasn't mounting / not being displayed in Finder.

After failed attempts of mounting & running first aid

@Bev_Tabet_Photo suggested downloading/updating the WD Driver (https://support.wdc.com/downloads.aspx?p=294) which I did, although I don't see how this would have played a role in fixing my issue, but it is something I did.

I then reset the SMC (https://support.apple.com/en-us/HT201295)

From here, I opened Activity Monitor and quit the fsck_ext process found under the 'disk' tab

This resulted in the external hard drive being "fixed", however it was only readable, and could not copy any files to it.

I ejected the disk, restarted, reconnected the drive and opened Disk Utility. I ran a new attempt at First Aid, which took a fair amount of time (10-15 minutes)

The First Aid was successful, and I was able to write to the external drive. So far, so good.

Hope this post can manage to help others. Merry Christmas!

Hi Paul, thanks for your help!

Mine is a Seagate Expansion 4TB external drive. I actually read in another thread that this problem could be due to operating system starting a disk checkup process (fsck_ext) when the external disk is connected. Problem seems to date back to last year when Mac OS Catalina was introduced, so it seems to not be issue with Big Sur exclusively.

This seemed to be the case for my disk too, as when I force quit that process (fsck_ext), I was able to access to access my files. However disk is now read only (and thus for example Time Machine says it can't write to the disk), so probably what I should do is to copy all content from it to another external disk (as I don't have that much disk space in my computers), format the disk and see whether it will start to work again.

I also read somewhere on this Apple Forum that users had left their external disk hooked to their computers, and after few hours (or in some cases I think even +10 hours) the checkup process had ran automatically and disk became accessible again. So I first tried with my MiniMac (which is running Catalina), left the disk there for few hours. Got back home and noticed that indeed the disk had become readable again, although the fixing process did not succeed as this error message was shown on the screen:

I also tried this with my Macbook which is running Big Sur, and received the same kind of message eventually after about 6-7 hours.

So anyway, it seems that one can access the files either by:

a) force quitting that disk checkup process (In Big Sur I had it named fsck_ext, in Catalina the process was not found at first, then I searched with only "fsck", and found somewhat similar process, I think it was calleeed fsck_htl or something, force quit that one and was able to get read access to my Seagate disk)

b) Attach the external disk to computer and wait until the checkup process is finished

For me at least, it seems that both options give the same result, read access to external disk. As it looks like the disk repair/checkup process was unable to "fix" my disk, so option a) would be the way to go, as it is significantly faster than option b), and user actually knows what is happening.

Anyway long story short, not quite sure how the drive is currently formatted, but here's a screenshot of how disk utility shows it:

If there is any way to get the disk fixed except by formatting, that would be awesome! There's currently about 3TB worth of data, including backups starting from 2018 so backing up that data first would basically require a new external disk (I may need to purchase another backup anyway, so probably not a bid deal).

My WD My Book wouldn't unlock, either. I ended up opening the WD utilities that came with the drive (if you don't have it you can download it from the WD website), then plugging in the drive to your MacBook. A window pops up asking for your password, then you can unlock it from there.

Finally I have access to my external HD and this is what I did however I do NOT think the update to 11.2.1 fixed it more the restart.

Leave the hard drive plugged in (mine is in a Dell Dock)

Restart your mac

a) Get your disk number

Note that your disk number can be gotten from following command

Replace KEV with your Disk name

❯ diskutil list | grep KEV

2: Apple_HFS KEV 999.9 GB disk2s2

Run the following command from terminal

b) Mount your disk from terminal

diskutil mount /dev/disk2s2

And finally it mounted and stayed mounted

UPDATE TO UPDATE:

It all seems to be working now. The HDD has been recognized now for more than 24hrs and has made Time Machine back ups every hour. Not sure why erasing the disk worked for me but it did. Like I said results may vary but here is what was wrong and how it worked:

1. After latest Big Sur update 11.2.1 one of my external drives HD Easystore 5TB HDD would not mount. It appeared in Disk Utility but not mounted. All my Time Machine backups showed inside TM?
2. Tried mounting via terminal commands and nothing would happen. Tried new cables and nothing. Tried the power up method mentioned here and nothing.
3. Installed latest software from WD and nothing changed. Tried erasing disk to start over but would received error that disk was not mounted and could not be erased or first aid.
4. Plugged HDD into another MAC also running 11.2.1 and it was not recognized. plugged HDD into a Windows computer and the drive showed up. I knew at this point it was a Big Sur issue.
5. I figured I had the back ups inside Time Machine so i decided to erase the drive while connected to the Windows computer.
6. Plugged the disk back into my Macbook Pro 16" 2019, and the drive showed up. Renamed it and tested dragging a file into the drive and it was visible so I decided to try a first new back up.
7. Back up took awhile but it found the drive, prepared the back up and backed up. It has done a back up every hour since then.

AGAIN, not sure why this worked but it did for me. Just sharing my experience. Proceed with caution.

How I wish i'd researched about Big Sur first before finally updating yesterday. I thought everything is okay by now since this has been available last year. Same issue here, I cannot see my external drive, instead I can only see an external drive named "Update". Because of this, and other issues on email, photos, missing folders and very slow speed, I reverted back to Catalina via Startup Disk (Catalina on Macintosh HD vs Big Sur on "Update").

Like the others here, in the Disk Utility, I was able to see my originally named external HD "Touro MacBook **". I used First Aid for the external HD but I still couldn't see it on Finder.

Here is the workaround I did to access my external HD files:

> in Disk Utility, right click on your external drive ("update" will be there too) and select Show in Finder.

> a Finder window will open your external drive and show folders App, boot, Lib, Sys, Users.

> unhide hidden folders by pressing "command shift dot"

> you will find a hidden folder named Volume, you should be able to see your Data folder in there containing your files.

This is such a hassle because you can only access your External HD via the Disk Utility :( it is the only place where I was able to see it. I hope "Big Sur" acknowledges this issue and finally provides a fix.

As I posted on another thread, I found a workaround, at least for the WD My Book drive. Maybe the same process can be used for other drives:

Open WD Drive Utilities

A window will appear with the message "Attach a supported WD Drive". 

Attach the My Book USB cable to the computer. 

Another window will appear with the "Unlock Drive" option.

Enter the Mac user password password, then clicked on "unlock drive". 

My Book For Mac then will appear in Finder and you can use Time Machine. 

You can also eject the drive from Finder.

I think the problem is that the Mac Os does not support the NTFS format, which compatible with Windows. I had a similar problem and tried to solve the problem through the suggested solutions, including using the disk utility and running first aid, but I did not succeed. The only way left was REFORMATING the External disk! Which was not really possible!

finnaly I found the solution and easily solved the problem by installing TUXERA software. Software that can run NTFS format disks on a mac book!

it’s really exciting and this way is the easiest way to solve this problem :-)

summary: Use TUXERA software!

UPDATE. I erased the HDD on Windows. Plugged into my MacBook Pro 16" 2019 and it recognized the empty HDD. I renamed the drive and picked it in Time Machine preferences and it started the first back up. This still sucks because it will take all day to do. We should not have to do these things for our products to work. I knew I had all my back ups from Feb 12 and prior before I erased the drive so I had nothing to lose. Proceed with caution if you try this. I will update this once my first back up is finished.

Found Solution

go to support.wdc.com download the WD Drive Utilities for Mac, after a few minutes my external drive were recognized

The download states it compatible up to Mac Lion, but it works for Big Sur

uploading all pics and videos to iCloud, never going to depend on hardware again.

Thanks to everyone for helping, my son passed at age 38 and had over 300GB of videos and pics on the external hard drive,

Thankfully I download the WD Drive Utility and few minutes later I had access to my external hard drives. The last week after uploading Big Sur I really thought I lost all my sons videos and pic 300GB. My son recently died at age 38 and the thought of losing videos from birth to age 38 would of been disastrous

thanks you again.

PS Apple very disappointed this is the reason I switch from Microsoft to Apple in 2003. We should have the option to reload a previous version if we are not satisfied with new version

Another Me Too. When I upgraded from Catalina to Big Sur, Finder no longer shows USB external drives.

I get some drives inevitably from Windows users, and so the disks are formatted with MS DOS/FAT.

The good news is that (1) Disk utility does show the drive, but more importantly, (2) I was able to find

the drive by going to Finder -> Go -> GoToFolder and typing "/Volumes". The FAT formatted USB drive

is located there and can be explored using Finder.

The big annoyance factor is that Finder is hot showing external drives on the left panel. I have "external

drives" set in Finder->Preferences (General Tab) and in Finder->Preferences->Side Panel. You can of course

drag and drop your USB drive to the side panel on Finder. And then it will show up, finally.

No hard disks, let alone External Drives, at all are showing in Finder, including the Macintosh Drive. While

everything is checked via Preferences, the side panel shows only Favorites, the iCloud Drive, and a list of

Tags.

Baffled that Finder default view usefulness has been diminished.

Thank you for your reply. I did not find an answer in the forum. However, I did solve the problem by calling an Apple repair shop (not officially Apple BTW). Here's what worked for me...Do a youtube search on how to perform a pram and smc reset. Both are absurdly simple and only take minutes. That instantly allow one drive to mount. Then, I had a pop up warning about NTFS for mac. I clicked on that and a previously undiscovered window appeared that allowed me to mount the remaining problem drive. It's amazing that this update has been out for SIX months and Apple has not issued a fix. They love appearance of being user-friendly but when problems happen, they just aren't there. I hope this fix will work for others.

Clarification: I meant originally when you first used it, not reformatting it now.

Try installing the latest driver for WD for Big Sur.. That’s what worked for me when the latest NTSF driver didn’t work. I’d basically given up and it appeared!

A final item for any who missed my fix: Try using the utilities that came with your external drive. Open the utilities app and then plug in your drive and follow instructions. That worked with my WD MyBook, but I realize it probably isn't the solution for other drives.