How do you eject a Time Machine drive safely?

Perhaps your issue is an improperly functioning system that is causing the problem.

Possible Fixes for El Capitan or Later

You should try each, one at a time, then test to see if the problem is fixed before going on to the next.

Be sure to backup your files before proceeding if possible.

1. Shutdown the computer, wait 30 seconds, restart the computer.
2. Resetting your Mac’s PRAM and NVRAM
3. Reset the System Management Controller (SMC)
4. Start the computer in Safe Mode, then restart normally. This is slower than a standard startup.
5. Repair the disk by booting from the Recovery HD. Immediately after the chime hold down the Command and R keys until the Utility Menu appears. Choose Disk Utility and click on the Continue button. Select the indented (usually, Macintosh HD) volume entry from the side list. Click on the First Aid button in the toolbar. Wait for the Done button to appear. Quit Disk Utility and return to the Utility Menu. Restart the computer from the Apple Menu.
6. Create a New User Account Open Users & Groups preferences. Click on the lock icon and enter your Admin password when prompted. On the left under Current User click on the Add [+] button under Login Options. Setup a new Admin user account. Upon completion log out of your current account then log into the new account. If your problems cease, then consider switching to the new account and transferring your files to it - Transferring files from one User Account to another.
7. Download and install the OS X El Capitan 10.11.6 Combo Update or 10.12.6 Combo Update or Download macOS High Sierra 10.13.3 Combo Update as needed.
8. Reinstall OS X by booting from the Recovery HD using the Command and R keys. When the Utility Menu appears select Reinstall OS X then click on the Continue button.
9. Erase and Install OS X Restart the computer. Immediately after the chime hold down the Command and R keys until the Apple logo appears. When the Utility Menu appears:

1. Select Disk Utility from the Utility Menu and click on Continue button.
2. When Disk Utility loads select the drive (out-dented entry) from the Device list.
3. Click on the Erase icon in Disk Utility's toolbar. A panel will drop down.
4. Set the Format type to Mac OS Extended (Journaled.)
5. Click on the Apply button, then wait for the Done button to activate and click on it.
6. Quit Disk Utility and return to the Utility Menu.
7. Select Reinstall OS X and click on the Continue button.

Hello,

To remove your hard drive using Time Machine do the following:

• Open System Preferences
• Click on Time Machine
• Click Add or Remove Backup Disk
• Click on the Disk you Wish to remove
• Click Remove Disk
• Click Stop Using This Disk
• Drag disk to Eject/Trash
• Unplug TimeMachine

I hope this helps and have a nice day

-Jacob

My Time Machine drive ejects without problems. You wait until the drive has stopped processing by watching the indicator light. Or eject the drive then wait for the OS to eject it. Spotlight's connection to Time Machine is what enables you to backup and restore. You can't search without Spotlight.

If you shut down the computer there is no reason to disconnect the drives. They will restart when the machine restarts. The official action is to select the Desktop icon(s) for the drive(s) you wish to eject then press the Eject key. You can also use Command-E to eject a selected drive(s) or select Eject from the Finder's File menu. Then there are ways using the Terminal.

As Kappy mentioned, ejecting a Time Machine drive shouldn't be a problem. I eject my WD Ultra on a daily basis without an issue. One thing to note, I do not have the drive added to Spotlight preferences. Perhaps that's the issue?

As a matter of fact I don't have Time Machine drives added to Spotlight > Privacy on any of my Macs.

Adding the drive to "Spotlight" / "Privacy" is supposed to stop Spotlight (through the mds process) trawling the drive.

I've been intermittently suffering a similar issue, and am looking for a solid fix as well.

Adding the drive into "Spotlight" / "Privacy" does help, but the setting seems to disappear from time to time. For me, the setting does become invisible whilst the drive is unmounted, and reinstates itself when the drive mounts, but occasionally when I eject the drive, I again receive the drive in use message. "lsof' implicates 'mds' as the culprit, and the drive has vanished from the "Spotlight" / "Privacy" list. On some of these sessions, I've verified that the drive DID add itself back into the list when it mounted. This means that either it was dropped from the list whilt in normal use, or, when I attempted to eject the drive, a race condition occurred whereby as part of prep for the eject, the drive was removed from the privacy list, and mds stepped in in the instant before the drive was actually unmounted.

Another mitigation that I've read suggests touching a .metadata_never_index file into the root of the removable volume (which is supposed to disable indexing the volume). I have implemented such files, but cannot say that I've noticed any benefit.

For me, the issue as noted on Sierra (which was the original OS on my MBP) and High Sierra since. However researching this suggests that it is a much longer running issue.