Resolved The given disk is in use by a driver - Time Machine

[djc6]

I purchased a Samsung T5 portable SSD for time machine. When I went to go use it, I selected encrypted backups. I received the following error:

There was an error preparing the Time Machine backup disk "Untitled".
The given disk is in use by a driver.

I found other mentions of this issue online, but no resolution so posting my solution here. I tried rebooting and using Disk Utility to wipe the drive - neither helped getting Time Machine setup.

Curious what was using the drive, I ran "sudo lsof" in Terminal to see what was using "/Volumes/Untitled". I saw two processes - "mds" and "mds_store" which are Spotlight related.

Going into System Preferences -> Spotlight -> Privacy and adding the external disk seemed to resolve problem for me.

 

[NoBoMac]

Or maybe a more manual way of getting setup?

When the prompt for "use this disk for Time Machine?" comes up, click no/don't use. Format the drive in Disk Utility. Select and encrypt the drive via desktop. Time Machine > Select Backup Disk.

This has always worked for me with no errors.