Disk utility wont repair external disk

Sier wrote:

use an external disk as my Time Machine that isn't working anymore because of a disk failure. I tried to erase this disk but Diskutility isn't able to unmount the disk, no matter what.

I would like, or should. Its a SDD disk, should have a long(er) life, I think...

Any other app for wiping the disk?

Disk Utility needs to be mounted to the drive in order to work on it.

If the disk is in use you can try from Terminal app to unmount he drive; turn off TM before you plug it back in..

copy an paste:

diskutil umount 

notice the trailing blank space in your copy and paste command line, drag and drop your external drive onto the Terminal window to complete the path and use the enter\return key to execute.

an example :

MacBook-Pro ~ % diskutil umount /Volumes/Install\ macOS\ Ventura

Volume Install macOS Ventura on disk2s2 unmounted

MacBook-Pro ~ %

turn off TM>Settings> turn off auto

plug the drive in and try again your DU>File>Force mount if necessary. Verify "Show all Devices."

You are erase/reformat/initialize as new, the parent (top most) drive not a Volume level, not Container level.

if I had a drive failure I would not trust it with my backups— any drive can fail, even new out of the box.

If you value your user data

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite. 

More than one device, more than one backup methodology.

Sier wrote:

I use an external disk as my Time Machine that isn't working anymore because of a disk failure. I tried to erase this disk but Diskutility isn't able to unmount the disk, no matter what. Also the partition method isn't working. The only lead I get is that unmounting isn't possible because the disk is in use of mds_stores...

replace the drive.