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

I am having what seems to be the same kind of problem. Very unreliable external SSD behaviour with Sonoma. My example is I bought two new 4TB SSD. I have a stack of these that I have gathered over time for Time Machine Backups. With Sonoma I am sometimes able to format the hard drives in Disk Utility, and/or initialize Time Machine on them from the System Preference. Sometimes it fails with "resource busy" like this:

When it does work, and I try to initiate the first backup for Time Machine it invariably gets to about 99GB and the stalls and fails. The only recourse is to reformat and try again.

I’m using a 4TB Western Digital storage drive which, after upgrading my Mac Mini to Sonoma, fails to “see” this drive. I have not had trouble opening and running Disk Utility. Having said that, it takes a few minutes for Disk Utility to have more than a blank window but when the various disks are eventually displayed, the storage drive is now visible and fully accessible.

The first time I noticed this issue, immediately after upgrading to Sonoma and the drive was not visible, I had to use Disk Utility to first find the drive and then also perform first aid but only that first time.

Now, it is normal practice to use Disk Utility to get the drive visible and It doesn’t matter whether I “eject” the drive before shutting down or not.

I only use a stand alone networked, I have been stable since Christmas reformatted all external drives and ssd's to APFS, things are working a treat! The drives are a lot faster, it must be something to do with the file system.

I've spent too much money and man hours trying to repair what is beyond my scope, I certainly am not in any hurry to update after the mess of Sonoma.

So long as my continuous cloud backups are taking place and Time Machine works; otherwise the Mac on my desk might just have an unfortunate accident and well I may have to replace it with something a little more reliable at present.

I've had problems with two external hard drives for some time.

The MacBook Pro M1 recognizes them and I can work with them, but it does not allow you to expel them or turn off the computer if they are connected (one or both).

It also doesn't allow me to apply "First Help" in Disk Utility.

It's as if a program was working with them and didn't allow them to be expelled, first aid, or turned off the Mac.

I just did a test on another old MacBook, with an operating system prior to Sonoma and the hard drives work perfectly.

It seems that it is Sonoma 14.3.1 that gives the problem.

Thanks for the suggestion. I have a 2023 Mac Mini M2. I have experienced Sonoma fails twice and my Sonoma fix, both times required a clean install of Ventura 13.6.3. Then the external connections worked again. With the exception of one problem, now the external USB-C 2-T NVMe drive will not shut off when I shut down my Mac. The drive gets hot and will finally shut off after several minutes. Before attempting the Sonoma upgrade, this problem did not exist. Some desktop Macs do not have the "Allow accessories to connect" option that began on Macbooks with Ventura (see https://discussions.apple.com/thread/254478957?sortBy=best for more on this issue) Since I dont have the courage to endure another Sonoma fail to see if this works for my Mac Mini, I am interested to hear if other users with a desktop Mac running Sonoma have the "Allow accessories to connect" option available?

I already back to Ventura and upto now no issue on it, but Sonoma having the issue for drives above 1TB, even with same enclosure 500GB and 1TB NVME working fine , when 2TB not recognise the drive, but other OS detect and working without zero issues as well as in Ventura, so I think Apple purposefully do this limitation to buy machines with high SSD capcity

HAd to power down yesterday... 

Didnt think anything of it as i have had to restart a BUNCH lately..and somehow was devoid of external HD issues...

or so i thought..

Upon the restart of the computer ALL of my external drives were GONE.

Took the USB HUB, mounted on my Monterey machine...NO DRIVES MOUNTING..

Remembered a post about going to Windows , did that and the drives are now back on Sonoma 14.4.

What the heck is going on ?? Unreliable OS that chooses to either see or ignore drives.... 

Come On Apple....

I'm going to post this again as it looks like my prior post was deleted.

I have M3 MacBook Pro. (AUD$4,800+) Worked fine with my LaCie 5TB rugged until Sonoma. Once I installed Sonoma it stopped recognizing it. As in immediately stopped working. Worked the minute before Sonoma. Did not work after Sonoma.

I spent a full Saturday on the phone with an Apple Engineer doing every single different thing to my computer - and they told me they could not figure it out. Recommended I get data recovery to try and save my files.

With no other options I purchased another new LaCie 8TB d2 professional directly from Apple ($600AUD). It is formatted exFat. It worked fine for a couple of weeks. Then the exact same happens. The computer completely stops recognizing the external drive.

I spend another full day with Apple Engineers. They ultimately tell me there is no fix and they need to escalate to a team of engineers and it will be several weeks. Still have not heard from them.

Calling them again today. Also have told them about this thread. 14.4 update does NOT fix.

Summary:

I've spent 2 full days over 14 hours on the phone with Apple Engineers.

They've told me they have no fix.

I've also called LaCie and they have told me there is no fix. They offered me a "complementary" data recovery on the 8TB hard drive which I bought less than 2 weeks ago. They would not assist me with the LaCie rugged data recover - that was a "too bad" response. LaCie said the same thing happened when Venture rolled out.

Apple - if you delete this again. I will repost it and I will find every single blog / review of computers / review of drives and paste this exact review over and over again.

I HIGHLY recommend not downloading Sonoma. Also as an FYI...M3s you cannot rollback to prior OS.

[Edited by Moderator]

Well, I also have this problem. There is no solution yet. I share my experience.

Previously: Kingston 2000 2 TB SSD worked on macOS for a year without any problems (and on ventura, and even on sonoma 14.1 for a while), and I also have a 2 TB Trascend HDD. My device - Macbook Pro 16 2021 1 TB. All these external disks were formatted after purchase in the format exFAT (to be available on both Mac and Windows).

A week ago, my SSD Kingston just started falling off, and my MacBook stopped recognizing it. I tried connecting it every now and then, either through a different cable from the HDD drive or through an adapter, but it was unstable—that is, it worked once and then it didn't work again.

1) At first, I thought the problem was with the storage device itself, but on Android, it connected quickly, and the files were transferred perfectly, without any delays. I mean, it works on Android.

2) Windows - I connected a ssd, it is recognized, but gives an error - and windows cannot fix it (as others wrote here that they managed to fix it this way - it didn't work for me) - that is, when connected, I had to choose "continue without checking for errors" and the folders open, but you can't copy them to Windows - it gives an error that the files are damaged. In this case, any file, even a video, even a small text document.

Therefore, it was not possible to extract the data using Windows. It doesn't work correctly (I think it's because of the disk format and MacOS was providing emergency assistance to the disk, so there are no permissions). I remind you that everything worked on the android.

3) MACOS - I have updated to sonoma 14.4.1 - and it doesn't work. The SSD blinks but is not recognized. And now my HDD disk takes a long time to connect - from 5-7 minutes until the Macbook recognizes it (before it was a minute, always!).

I restarted the system from safe boot mode via text support, and it also doesn't see the disk, but after restarting in normal mode, it recognized the disk once. In this way, I managed to copy the files to my disk. But the Finder started to freeze. And yes, after restarting, nothing works again. I repeated the event through this boot, then a normal reboot - and again the ssd started for one time. After disconnecting and reconnecting, it is no longer recognized. Emergency assistance is not provided - it also freezes, and the disk utility sometimes loads, sometimes not. In general, it doesn't work!

4) I tried to connect this SSD to my friend's MacBook, which has an old version of MACOS (9th or something), and it doesn't recognize it either.

....

So I don't know what kind of trouble it is, but looking at the stories of others, I'm sad that after spending a lot of money on equipment and disks, I can't work and it's not fixed by updating the system... Moreover, it happened suddenly and not even after the update, but until then it had been working for a year without complaints.

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]

UPDATE: just happened to eject the drive in macOS and reboot and the drive did not appear and started the smart scan again and slow to mount, formatting to APFS and copying everything...

Yes I formatted my external hard drives in APFS. Seems a bit faster too.

trata de volver a la versión ventura. esa es la solución a todos los problemas.

Start my old PC Window 7. Connect external SSD. Check SSD. Fix the issue. 2 minutes to repair. Thanks Microsoft Window.