I'm setting up Time Machine backups on a new external hard disk.

I chose to first encrypt the disk via Disk Utility:

But I also see these options:

Is there any difference between an "Encrypted" format via Disk Utility and selecting "Encrypt backups" in the Time Machine preferences? What happens if I do both? Or if I encrypt with Disk Utility, but then don't select "Encrypt backups"?


Aha! The answer comes when you try to deselect the "Encrypt backups" option:

So it appears they are one and the same.

  • Could you clarify that you got this question on a disk encrypted with Disk Utility and not from Time Machine? – dan Oct 5 '16 at 10:23
  • If you deselect "Encrypt backups" Time Machine will show this prompt, but it's unclear what entering the password and selecting "Turn Off Encryption" actually does. I tested it and it seems it reformats the backup partition to be unencrypted at the filesystem level. – augurar Dec 23 '18 at 1:18

The command:

diskutil list my_time_machine_disk_short_name

will confirm you:

#   my_mac:/Users/bob  % diskutil list disk5
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                 Apple_HFSX Time_M___disk          *499.4 GB   disk5
                                 Logical Volume on disk2s2
                                 Unlocked Encrypted
#   my_mac:/Users/bob  % 

that Time Machine is using the same technic of logical volume as Disk Utility.

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