Disk Utility can't umnount ext HDD's with First Aid

The latest OS works much like the old but with a different user interface. I have not seen any difference in the Disk Utility interface. Boot into safe mode and see how the drive acts. Then if OK reboot normally and test.

Start up your Mac in safe mode – Apple Support (MY)

Although the info from this link ( below ) pertains to a Third Party Cloning Software

The focus of Unmounting an attached External Drive remains the same

https://support.bombich.com/hc/en-us/articles/20686422368663-Why-can-t-I-eject-the-destination-volume-after-the-backup-task-has-completed

It's usually Spotlight

More often than not, some Spotlight process is retaining an open file on the backup volume and preventing it from being unmounted. If you find "mds" or "mds_stores" listed in the lsof output, you can disable Spotlight on your backup volume to prevent the interference. To disable Spotlight:

1. Click Volumes in CCC's sidebar
2. Select your backup volume in the sidebar
3. Toggle the Spotlight switch to the Off position

Mike Stand wrote:

They're not being used by any open application that would be using the three drives I had connected at the time when I discovered this issue. Unless there is something the OS is engaging them in, like indexing that AI mentioned as one possibility.

My last OS was High Sierra. What's going on nowadays with OSX is completely new territory to me.

I do mainly home audio recording (DAW) so I have external hdd's formatted HFS+ that's used for sound content.

This command lists open files on a drive:

sudo lsof | grep /Volumes/diskname

You can kill processes that are tying up the drive(s) through Activity Monitor. Often these will be one of the mds processes (Spotlight). However any number of antivirus, app cleaners, "Defender" or other security tools, can cause a disk to be tied up and not ejectable. Those security, antivirus, "cleaner" apps are all unnecessary and can cause harm by interfering with external disk management as mentioned above.

In the past (not sure it still happens), MacOS had a bug where one of the QuickLook related processes would tie up a drive, such as QuickLookSatellite, QuickLookUIService. These will show up in the lsof command above and can be killed off in Activity Monitor.

If you have any DAW related software running in the background, it may remain connected to those drives and prevent ejection. Even if you have quit that DAW software, its extensions may still be active in the background and connected to one or more drives, preventing ejection.

Mike Stand wrote:

Thanks for your help. :)

Haven't gotten around to installing a cloner. I happened to use Superduper myself.

As I said to steve626 below...

Now that I know it's not my devices, I'm ok with leaving things be and not messing around with anything. I use Disk Warrior anyway 99.9% of the time and had no issue with that unmounting a disk

Are you specifically saying Spotlight is not the cause of this issue

Regardless if one uses CCC or Shitpockey SD which seem the main focus in above

Spotlight will attempt to Index ir reindex " I do mainly home audio recording (DAW) so I have external hdd's formatted HFS+ that's used for sound content. "

This is unless, one specifically excludes that drive from Spotlight

As of now you can't clone a Silicon Mac like you can an Intel Mac.

I use Carbon Copy Cloner and when I had trouble cloning my Mini M4 I contacted CCC customer support and the following is what they reported back to me on how to clone a Silicon Mac:

"Apple's APFS replication utility is consistently failing, it's not going to be able complete this task. I wish I had any insight at all into what kind of corruption it's finding, how serious it is, etc, but Apple's tool just doesn't provide that level of detail.

So, on to plan B:

1. Boot into Recovery Mode

2. Erase the external disk in Disk Utility

3. Install macOS on the external disk

4. When the installation has completed, accept the offer to migrate data from your original source disk

Best wishes,

Rob

Bombich Software, Inc."

Old Toad wrote:

As of now you can't clone a Silicon Mac like you can an Intel Mac.

I use Carbon Copy Cloner and when I had trouble cloning my Mini M4 I contacted CCC customer support and the following is what they reported back to me on how to clone a Silicon Mac:

"Apple's APFS replication utility is consistently failing, it's not going to be able complete this task. I wish I had any insight at all into what kind of corruption it's finding, how serious it is, etc, but Apple's tool just doesn't provide that level of detail.

So, on to plan B:

1. Boot into Recovery Mode

2. Erase the external disk in Disk Utility

3. Install macOS on the external disk

4. When the installation has completed, accept the offer to migrate data from your original source disk

Best wishes,

Rob

Bombich Software, Inc."

https://discussions.apple.com/content/attachment/a98056e4-5e0c-47d9-a8f6-555d1cfd12d4

Amen to Bootable Clones on Silicon machines

https://bombich.com/blog/2024/12/19/bootable-backups-have-been-deprecated-for-several-years

It will not unmount if the drive is in use then you must do it manually.