Delete backup from external.

It is a bad idea to delete any single backup from your Time Machine backups.

If you want to erase the external drive and start over or use the external drive for something else?

Then you will need to use Disk Utility and totally erase and format the external drive.

see > https://www.hellotech.com/guide/for/how-to-format-a-hard-drive-for-mac

If you want to make Time Machine at best unstable and at worst lose all of your backup, then begin removing backups! Seriously just don't do it. If you need another EHD with more capacity get one and move your TM backup to the new drive. This is easy to do and there are many articles that explain the proper method for doing so.

If you leave TM alone it will automatically remove the oldest backups with no user intervention.

solaskisix wrote:

Can the EHD with the backup be removed and reattached at intervals? Thanks for the input.

Yes you can removed and reattached your Time Machine drive, but only if you disconnect it for short intervals.

If you leave Time Machine disconnected for too long, then (as you found out) Time Machine can not do normal incremental backups and wants to do a new full backup when it is reconnected.

Best bet is to just leave your Time Machine drive connected to your Mac and let it do it's work.

Or.... if you want a more flexible backup that you can connect and update at will, then you will need a different type of backup like CarbonCopyCloner or SuperDuper.

https://bombich.com

https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html

Time Machine does not and should not make a new full 600GB backup each time it backs up. It should make the initial 600GB backup and then only make small periodic backups of the changes after that.

see > Back up your Mac with Time Machine - Apple Support