External SSD corrupting after after upgrading to Sonoma.

Turn off Spotlight for disks formatted as ExFAT. That fixed this issue for me. I have several hard disk drives formatted as ExFAT (for Mac & Windows compatibility), and they were slow & crashed under Sonoma until I turned off Spotlight for those disks. My ExFAT disks were actually getting corrupted by Spotlight, so it wasted a lot of my time.

To do this: In Sonoma system settings, go to "Siri & Spotlight", and then "Spotlight Privacy". Click "+" to add the ExFAT disk(s) you want Spotlight to ignore, then click "Done". After doing that, searches on the ExFAT disks will be slower, but at least your computer won't hang/crash/etc. I hope this helps.

I have several Crucial external SSD, but none is formatted as ExFAT. They have all been working fine with Sonoma.

I suggest that you copy the contents of the SSD to some other drive, then reformat the drive as ExFAT, since that is what you need. It is probably better to format in the Mac, apparently (this is what I have gather from several previous discussions, though I never had to deal with this back and forth between mac and pc).

Here's my recent scary experience: My external hard drives, mechanical, have failed to mount on my Mac since I upgraded to Sonoma. My drives were formatted in exFAT. I think lots of people are seeing this same problem. Had to use EaseUS software to get into the unmounted drives so I could copy files. I'm now reformatting all my external drives to APFS.

I see you are needing something like exFAT so the drive can communicate with both PC and Mac, so I'm not sure what the answer would be. But just want to let you know that Sonoma is showing problems with exFAT drives.

Josesuarez3... Have you found a solution to your problem with SSDs on Sonoma? I wish I had seen this before recently moving from Ventura to Sonoma 14.3, but didn't. Did you move back to Ventura? I'm not even sure if you can, as I've seen conflicting info on that possibility. I hope Apple finds a solution very quickly!

Please keep me updated with regard to any new changes (positive or negative).

That's an excellent suggestion, Peter. I would act on it immediately, but I have already solved the issue another way [I think]. I have two SanDisk 4TB Extreme Portable SSDs. I had formatted one as ExFAT and the other as Mac OS Extended/Journaled... each for different back-/cross-compatibility scenarios. Both contained > 3TB of data on them. I eventually reformatted some older pocket drives in order to backup the SSD data [in parts]. I then reformatted both SSDs to APFS and merged the original data back to their respective drives. This only took about two full days and nights ;-(

I've been playing these games with Apple since "System 1.1" in the early months of 1984. No doubt I've forgotten many of the issues I had to deal with back then. "System 1" and "System 2" have somewhat faded in my memory. But one thing I do recall is that, unlike Microsoft, Apple used to do their own "Beta Testing".

Since both of my SSDs are already indexed (and cooled down), I think I'll leave them under Spotlight's supervision. They are both "reference drives", full of PDF books that I've acquired (or self-created) over the years. Having the content OCR'd and the drives indexed allows me to search my entire collection for any given word or phrase (and also for any and every additional drive that is so connected). Removing Spotlight would negate that incredible power! This is critical for me, as I am typically off sailing in the Bahamas and beyond, with only limited access to the Internet.

Anyway... I thank you for the tip!

Yes, that is what I was suggesting.

I'm hoping that some of the slowness is due to reindexing for searches. This is typical with a macOS update.