Using Big Sur need to fully delete and remove partitions on external SSD

MacL wrote:

I want to back up my laptop and then erase and start it fresh with current OS. I bought a HP P500 SSD to use to back it up. I finally got it set up in APFS. I don't know how, but I now have three partitions or volumes? that are the same size as the hard drive. I don't want anything but an empty space with no partitions or volumes or containers etc so I can create a time machine back up. I can't use the "-" in partition... it is greyed out. Also.. erasing the top level HP500 name on the left hand side... doesn't remove the partitions... it just keeps adding more. What am I doing wrong? I just want it to be APFS... and otherwise nothing else.

Volumes share space within the same Container with no penalty— therefore use the +/- to remove Volumes

ref: Add, delete, or erase APFS volumes in Disk Utility on Mac

If multiple Containers (read partitions) then erase/reformat/initialize the drive as new to regain all storage space

Disk Utility>View >Show All Devices this wouldd be the parent drive (top most.)

Erase and reformat a storage device in Disk Utility on Mac

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Apple provides a very good backup Utility named Time Machine, already built in to MacOS.

Time machine runs at low priority in the background, so as not to interrupt your work. It saves backups of only changed files. But rather than discard backup history, it keeps both the latest backup and previous saved files, in a database. Oldest copies are consolidated when space gets tight. This means it can retrieve files as of any day that is still retained in the backup set.

If you are going to use Time Machine, when you specify the drive as a backup destination, Time machine will often invoke Disk Utility and re-initialze the drive to its liking.