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, I just wanted to document my current status with the external hard drive issue.

I had four EHD and lost two of them at the Big Sur 11.1 update.

A 1TB Seagate Back Up Plus for Mac and a 1TB Seagate Expansion Portable Drive continue to work.

Lost the older 3 TB WD My Book Essential and a 5 TB Seagate Expansion Desktop Drive.

Things I've tried that haven't worked so far:

• Neither drive is visible in Disk Utility
• SMC reset: https://support.apple.com/en-us/HT201295
• I've looked for Seagate and WD driver updates for Big Sur but nothing is available at the moment
• I've downloaded both the Big Sur compatible Seagate Paragon and the WD Discovery "general" drive management software
• https://www.seagate.com/ca/en/support/downloads/
• https://support.wdc.com/downloads.aspx?lang=en
• Neither drive was visible from the Paragon software
• The WD Discovery software could see the My Book drive but showed it as locked. I've never set a password and from what I've read there is no way to unlock it without the drive booting/already having access
• Downloaded iBoySoft NTSF for Mac but neither was visible

So based on what I've read I either need to get another Mac with an older OS and transfer the contents of the old disks to newer/compatible EHDs, or wait for Apple to patch or wait for Seagate and WD to update the drivers.

I've completely read through this support thread and If anyone has any other suggestions I would love hear them.

Hi Apple support! I am having the same problem with my Macbook Pro and my Seagate 4TB external hard drive. It no longer shows up at the Finder, although I can see the disk with Disk Utility tool. But it can’t be mounted. This is unfortunate since I have tons of important files on that disk and also all my backups. I hope a fix is coming soon!

Same here. After installing Big Sur on my relatively new MacBook Pro (2019), my hard drives fail to show up. First it was one out of three, and now it is two out of three. No matter what I do (restart, shut down and start all over)...nothing seems to make them show up. They are on, through a powered USB hub, and I can see their blue operational lights. Disk Utility does not seem to see them either.

Anyone? Anything?

I upgrade to Bug Sur last night and I am having the same problem with my MacBook Pro and my Seagate 4TB external hard drive. It no longer shows up at the Finder or in Disk Utility tool or in Stellar Photo Recovery. I tried 6 different cables and 3 different USB ports with no luck. I updated to the latest driver for Big Sur and still nothing. Going to try another computer to see if I can upload the images to my cloud from there, but would like to use it since all my RAW images in Light room refer back to that disk.

Apple support personal are not here. We're all users like yourself. If you want to contact Apple directly and tell them about your problem use this link: Feedback - Photos - Apple

How is the drive formatted?

Can you see it with Disk Utility?

I'm having trouble mounting 2 external 2bay hardware RAID drives. Formatted in disk utility, but then gone. For full description, see the following link:

Big Sur Thunderbolt 2 - External Drives-not recognized by multiple Macs.

Not sure if this is related. Interesting that my drives will mount just fine in USB, but not TB2.

Hello Big Sur 11.2 users with questions I just looked at this:https://discussions.apple.com/search?page=1&q=Uninstall%20Big%20Sur%20OS%2011.2&content=filterDiscussions

And the variety of issues is too large to fathom. Inexcusable. I will be posting for help in how to uninstall this OS and go back to Catalina, as is mentioned by one person on the threads.

Epiphany-uc wrote:

Helpfull button won't function in this thread? Why not? Thanks for your post. Sounds incredibly beyond my abilities. BTW just found my old Time Machine. It will not mount. Never even asked to enter a product key. Beyond awful.

https://discussions.apple.com/content/attachment/6a85805b-82ea-4ad1-9c16-8f4d13976f41

Ne

says NTFS, (New Technology File System) is a proprietary journaling file system developed by Microsoft. 

Big Sur is compatible https://www.m3datarecovery.com/ntfs-mac/ntfs-for-mac-big-sur.html but clearly somethings wrong.

Hey Xenocide38!

Well done! I think, however, when running a disk repair, “First Aid”, it’s best to do it while booting to the recovery partition. This way, you are not booted from the internal, or external drives. I’ve seen repairs/erases/etc. fail when run while logged in, yet work fine while in recovery mode. (Single user mode was discontinued years ago, unless you still have an older Mac with an older OS, but you can boot to recovery mode now if you need to):

https://support.apple.com/guide/mac-help/about-macos-recovery-mchl46d531d6/mac

Otherwise, hope your trick fixed it! That’s good to know!

Hey there!

Good question. If you didn’t have a backup while on a previous OS version, then you’d have to create a bootable installer with a previous OS, boot from that, erase the HD, then reinstall the older OS. In either case, to downgrade the OS the Mac does have to be erased, so you’d probably want to back it up first.

Once you have the previous OS installed, you can migrate the data back onto your Mac.

How to create a bootable installer for macOS

https://support.apple.com/en-us/HT201372

How to get old versions of macOS

https://support.apple.com/en-us/HT211683

How to erase an Intel-based Mac

https://support.apple.com/en-us/HT208496

How to reinstall macOS

https://support.apple.com/en-us/HT204904

Move your content to a new Mac

https://support.apple.com/en-us/HT204350

Hope some of that helps!

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.

I work on a variety of machines ranging from Windows PC to Apple Built Mac\win to Hackintosh. I recently restored a MacBook Air 2013 that a child uses for schoolwork, and updated it to Catalina. Everything was fine until the kid updated to Big Sur.

I used a third party, "Compatible" disk, that wasn't "completely" compatible, but only found out at the time of the restore. The problem at the time was that the disk was PROVIDED by my clients, not by apple. Every other manufacturer uses a WIDE STANDARD for compatibility. Apple made the mistake of NARROWING from their stated compatibility; the reason for it is unimportant, they flat out lied to the entire world, not a small community. Not a happy event. They did, eventually revert to a wider standard with a later firmware\SMC combination. This allowed me to use an old, used disk (I purchased from a friend who had wiped his old MBA disk after the MBA suffered a main board failure) to update the machine, and transfer to the new disk, though it took a serious reworking of the whole process. I had to use the old, low space hardware to install to the new hardware, Via a restore process. It worked.

1. Install Mac OS onto one internal disk
2. Run the installer to install to a second disk\partition
3. Run disk utility to restore from the second disk to the third party disk, along with the EFI partition etc
4. Set the machine to boot from the new, third party disk

It worked for more than 6 months on Catalina. Updating to Big Sur killed it. Now at boot up, I can see the disk when I press alt. However, I cannot get it to boot. I cannot get the internet recovery environment to read the disks either. It won't show the usb external no matter what I do. They work fine on other machines, even in windows with special APFS\HFS drivers. They are seen by "SYSTEM REPORT" in Mac OS, but they are not loaded in disk utility or in the finder. All Darwin command line commands don't see them either.

I've tried many old MBA disks (apple branded) and they do not show up unless internal to the machine.

Big Sur has KILLED USB or rewritten it's protocol somehow, making it impossible for older machines to utilize.

First, in the menubar for Finder, click Preferences.

Make sure "External disks" is checked. This is for removable disks like you mentioned. "Hard disks" is primarily for fixed drives.

If it is already checked, does the external drive display within Disk Utility? If it does display, try erasing/reformatting the drive under disk utility.

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).