Unable to access External Drives and Disk Utility after updating to macOS Sonoma.

Beyond frustrated I have spent almost two days trying to trouble shoot this issue, my drive went from working to not working in a matter of two days. Thought it was my ports now I understand it was the update. This is not a good way to keep people in the ecosystem, force is never a good strategy.

Hi! I just recently upgraded from a MacBook Air 2017 to the new MacBook Air M3 and I also have this problem. I have an external drive for a few years now where I storage essentially old pictures and important documents from university. The drive was already formatted once since I had it before migrating to apple, I used it with my windows PC; it worked well with my Mac Air 2017 since then. Now that I've upgraded to the Air M3, I just can't read the external drive, I even tested the USB-C adaptador I bought, it works well with PEN drives, it just doesn't read my external drive :( I also tested my drive on my surface PC and it did not accuse errors. I don't know what to do.

to the people who have lost recognition of their external hard drives when using Sonoma OS: this also happened to me, and neither apple care or the apple store could help. they both told me the HD was fried. Fortunately, I have a friend who suggested hooking the HD to his computer using Linux OS, and there was my HD on the screen, with all it's contents. I emptied that HD into another, then reformatted it, and when I plugged it in to my new mac mini 2, it was again recognized and works perfectly. hope that helps--if you can find someone who has Linux and knows how to use it.

I believe problem with the data indexing algorithm, when you plug-in the device. If you have an empty storage, you will see all your disks almost immediately. But if you have big storage and big amount of files the drive will not be mounted until everything got indexed.

From this point I believe Apple Sonoma OS developers should look at the mounting strategy and do all indexing works in background, not on the moment of mounting the disks.

For those who has a lot of files and if they are big - be patient and wait until everything appear, once you have plugged-in. Otherwise you will lost your data.

Same issue here on Mac Studio running Sonoma 14.5. I tried 3 different SSDs (Samsung, WD, Kingston) and 3 different external enclosures (both usb-c and usb-a). Doesn't matter if it's an Apple Journaled disk, FAT, NTFS or anything. I tried them all...They worked for a day or two then gone. Disk Utility and System Report don't even recognise there's a drive attached. The drives and enclosures all work perfectly fine on separate Windows and Linux machines so this is clearly an issue from the OS.

[Edited by Moderator]

THIS WORKED FOR ME!

Here is what I did to get my 4TB LaCie mechanical drive to be recognized by Sonoma 14.2.1. I call out my mechanical drive because I also had an SSD drive not mount, but I think it just bit the dust.

When I got my mechanical drive, I formatted it Mac OS Extended (Journaled). To my understanding, this is fine formatting for a drive that will be used solely on a Mac and is compatible with most versions of Mac OS.

For this explanation, I will speak to what I did for the mechanical 4TB drive because my SSD drive never mounted on anything—it's a goner.

I started by finding a machine running a much older version of Mac OS. I happened to have an old laptop running Mojave. After it took ten years to boot up, I hooked up the drive and it mounted, but it wouldn't index the drive. I could see root folders but nothing inside. I opened Disk Utility and saw data on the drive because it showed how much space was occupied on the drive (in my case, 612 GB). I didn't attempt to repair the drive.

I then closed Disk Utility, right-clicked the drive icon, selected Get Info, went to the bottom of the window, and toggled the Sharing & Permissions carrot. From there I clicked the lock icon and unlocked the sharing and permission preferences. I then check the box next to Ignore ownership on this volume. I then clicked the lock and locked the setting.

After that, I restarted the laptop. Once it fully rebooted, I went in to double check that the box was still checked next to Ignore ownership on this volume. I had to perform this step (check the box and restart the laptop) a couple of times, but it finally took and remained checked. Once the setting was retained, I shut down the laptop running Mojave and moved over to my machine running Sonoma.

On the laptop running Sonoma, I made sure to remove items launching at login. I didn' want anything impeading the mount of my hard drive at startup. I then hooked up my drive and it mounted.

I hope this helps information is helpful for you.

A FEW NOTES:

I came to this realization becasue ALL of my current and old Time Machine drives ignore ownership and they had no issue mounting on my Sonoma laptop. So, I figured if form follows funtion, I replcated the same settings on the drive not mounting and it worked.

I am seeing a lot of callouts regarding ExFat drives, APFS and other sorts of drive formats...I can't speak to those specifics, but I would attempt to perform the simple (althought it took me hours of trial and error to figure out) process above and hopefully you'll be up and running in no time.

Cheers!

I now don't know what to do... I have had two USB-C Crucial 2TB SSDs corrupted by Sonoma 14.1.1 - possibly recoverable but I have lost all confidence in using them on my MacBook Air - these were being used to try to recover a SanDisk 128GB MicroSD card from a Nextbase Dashcam - I wasted hours trying to figure out what had happened to that - I now suspect it was Sonoma that corrupted it too. I've had cases where this and the Crucial's would show as unmounted but then find First Aid/fsck would be needed on next mount... 

we need to know when it is safe to use exFAT on Sonoma else at least for me I am going to have to switch to a W11 laptop for anything I need to do with exFAT... something I never thought I'd say that W11 would be a better and more reliable option... please be upfront and explain what is happening and when it will be fixed - I see many others with the same issue. Thanks

I saw in the release notes for 14 this:

• The implementations of the exfat and msdos file systems on macOS have changed; these file systems are now provided by services running in user-space instead of by kernel extensions. If the application has explicit checks or support for either the exfat or msdos file systems, validate the applications with those file systems and report any issues. (110421802)

[Edited by Moderator]

Glad to hear you figured things out. I wish Apple would say something to warn people.

This did not work for me. My external drive is not visible at all in macOS. I can only see that the USB plugged in System Reports under the USB tab.

What looser at the Apple company is responsible for this mess up?

Do we all have to change to microsoft to continue?

Use softwareupdate in Terminal.

To list available installers:

softwareupdate --list-full-installers

To download a specific version,

softwareupdate --fetch-full-installer —-full-installer-version 13.6.2

I run a Sabrent 4 bay external that does indeed act up on occasion, like individual drives dropping off.

Sadly, as the Mini i have only has 2 USB ports i use an Powered extender Hub (that works flawlessly with Monterey on the older Mini) that also had to host my Scarlett 18i20 audio interface (which also ran flawlessly on Monterey).

HAd top move the Interface to its own USB port as it seems the OS cannot handle it when it is on the Hub..

It will show that it still has Sync-Lock yet it will not pass audio - unless its in the Unique USB.

I see so many complaints about the ability of Sonoma to simply do its job..

Many regrets for "updating" - have wasted Hours with the new "features" as so many of us have.

Wish Apple could truly Upgrade rather than sending a new OS out to the real users - who find the problems their highly paid Engineers dont.

I dont like being a Guinea Pig, I want a product i can believe in again.

M1 MBA 2TB NVME SSD is not supported by macOS Sonoma, its mount once and when eject again its impossible to detect by OS, if its connected with some other OS like android in mobile then again connecting with Sonoma.

If I tried to copy large file its stoped and crashed and stoped working after around 25GB but this drive worked before without any issues in Ventura, after several updates in Sonoma upto 14.3 wont fix the issue, So I installed Ventura again drive working perfectly fine, I'm back to Ventura but when compare to Sonoma I felt my MBA M1 works speed and I think Sonoma limit the speed of M1

As new FEATURES appear in 14.2.1 (and we certainly hope the updates DONT cause NEW ISSUES....

i have just had a solid Open Office document refuse to save due to Sonoma claiming the document was opened by an UNKNOWN USER...

i read and write to that document daily...

maybe its time for some Class Action towards Apple for the unbelievable grief so many of us are being served all because we have been taught to believe UPDATES FIX THINGS ...when clearly , with Sonoma, they do not.

One Used to be able to rely on Apple products....

i am so very close to going UBUNTU!

Last update NOT SOLVE the problem .

Only slow down the Mac.

the update brick the system during startup.

after 3 reboot the Mac works . But is slower than before.…. and sure I had to wait one hour to see the hard disk

my advice is stay miles away from this OS.

Expecially if you work with your Mac