clayton1229 wrote:
The drive is exFAT. Not sure about 3rd party utilities, it's a Samsung T9 external SSD, no external power supply & no hubs. Safe-boot doesn't help.
The data I'm working with has several hundred thousand files on the drive, so perhaps that's contributing to things? When I plug the drive in, I do see a fsck_exfat process in Activity Monitor taking up 100% of a CPU core. When I do "ps -ef | grep fsck" in terminal, I get this:
0 2313 330 0 10:25PM ?? 73:53.42 /System/Library/Filesystems/exfat.fs/Contents/Resources/./fsck_exfat -y /dev/rdisk5s2
Those are red flags that the disk has failed or is failing. First, Disk Utility hanging when attaching an external drive is a symptom of a failing external drive. Second, when MacOS detects a failing or damaged disk, it will run fsck automatically when the drive is connected, before mounting it. That can take a very long time with a large drive like yours, and also a damaged drive can take a very long time for fsck (fsck is the file system check utility; it is actually used by Disk Utility as well when checking a drive) to complete, after which the drive will mount.
One thing you can try is to kill that fsck_exfat process in Activity Monitor; some have reported that this enables the drive to mount immediately. But it will still be damaged and this would be the time to try to copy everything off the drive asap to a safe place. You can then decide whether to reformat as Matt suggests or simply get a new drive.
By the way, if you are using third party drive utilities for the drive, if they are out of date or not fully compatible with Sonoma, that can produce the type of behavior you have seen, which is similar to a failed drive. The cure in that case would be to update the software or firmware, replacing or reformatting the drive night not be necessary. This is one reason that third party drive utilities are not recommended.
