Formatting Time Machine external drive

APFS is principally meant for use on SSDs. Although it will work on Hard Disk Drives, it was not designed for such use. Given the mechanisms used by Time Machine, I would use HFS+ unless you are using SSDs for the backups.

As a side note— I would not put all of my backups in Time MAchine which is great when it works.

You can read more if you google: "3-2-1 Backup Strategy"

three copies of your data, two different methods, and one offsite.

Boot clone https://discussions.apple.com/docs/DOC-10081

How to use Time Machine to back up or restore your Mac: https://support.apple.com/en-us/HT201250

Use DiskUtility Restore feature https://support.apple.com/guide/disk-utility/restore-a-disk-dskutl14062/mac

Regardless of what the Apple representative told you, Time Machine can only back up to external drives formatted in HFS+ (aka, Mac OS Extended), NOT APFS.

Thanks very much. I am paranoid about backups, so I keep two TM backups (home/office, almost identical) and my most critical data lives on box.com besides.

I'm just trying to juggle external disk drives, whose number keeps growing, as does their physical storage size over the years. And have been pondering moving my TM backups to a larger drive to postpone erasure of earlier backups. I have a 1TB internal drive on each machine, but am close to maxing out my 2TB external backup drives. There's always the question of diminishing returns—how far back do I really need to go in time. But a 4TB x-drive might make sense.

What I don't have is a bootable clone for either machine; that would require an additional pair of drives. I suppose I could limit it to one (the most used) machine as an extra safety measure.

Such a complicated world!

found it.

Thanks, very sensible sounding.

My thoughts are as follows:

• • One Time Machine Backup
  • One Bootable Clone Backup
  • One Cloud Backup

More backups are desirable but budget restrictions often prevent that. So, I think if you can handle three backups, then they should be done on separate drives using two different utilities. In your situation, you have Time Machine and a second utility. I would recommend using Carbon Copy Cloner. Your third backup is in the cloud.

Did you know a Time Machine backup is bootable? It will boot from a copy of the Recovery HD into the Utility Menu from which you can restore a Time Machine backup.