Cannot format external HD to HFS+ (encrypted) for Time Machine

How to make sure Time Machine works when you upgrade your hard drive may provide additional useful information. However, lllaass' suggestion to archive earlier Time Machine backups sounds like the most straightforward approach.

I recall that I once tried to continue Time Machine backups on the same volume after an OS upgrade. While the backups from the previous version of the OS were retained, I couldn't use Time Machine restore for the older backups (although I could copy files using Finder). I ended up erasing the entire volume and starting a new set of backups.

Thanks for sharing your experience. When you restored the file, did you use the Time Machine Restore capability or did you simply copy the file from the (HFS+) backup volume using Finder? I'm asking because in my case, I found that I could not restore files using Time Machine Restore from a backup made using an earlier release of macOS. On the other hand, I believe that Time Machine backups did continue using the same volume from the earlier release. Eventually, I erased the entire volume and started a new set of backups.

BlueberryLover wrote:

Thanks for sharing your experience. When you restored the file, did you use the Time Machine Restore capability or did you simply copy the file from the (HFS+) backup volume using Finder? I'm asking because in my case, I found that I could not restore files using Time Machine Restore from a backup made using an earlier release of macOS. On the other hand, I believe that Time Machine backups did continue using the same volume from the earlier release. Eventually, I erased the entire volume and started a new set of backups.

https://discussions.apple.com/content/attachment/c3b61887-731b-41ae-81b0-d2f130ff714a

I restored the files by entering Time Machine ("Enter Time Machine" from the drop down Time Machine menu item), with its spooky outer space like interface, going back using the bars on the right to a very old backup that predated the upgrade to Monterey, and selecting the files to restore. Since those files already existed, I selected the option to keep both the original as well as the restored files, they were identical. I did not use the Finder for this although I believe that should work also.

Another test of this came from my other much older 2013 MacBook Air. It was on Catalina, again with two HFS+ Time Machine disks. It was upgraded to Big Sur in December 2021, and for that Mac Big Sur is the furthest it can go. I kept using one of those HFS+ Time Machine backups but reformatted the other to APFS so for that backup disk the oldest backup is from Dec 2021, while the HFS+ one goes back years. I can restore from very old backups on the HFS+ backup in the Time Machine interface (Enter Time Machine). Using the Finder to simply copy a backed up file also works (on either backup) but is less fun.

I think this is the way it is supposed to work, not having to use the Finder to restore files but instead being able to Enter Time Machine with its special interface and restore from that. It's more work to restore by copying in the Finder, but that's also an alternative.

The Terminal command tmutil has many options and may be able to create a Time Machine volume with the attributes that you're looking for.

It seems to me that I could keep using an HFS+ formatted Time Machine volume in Big Sur. However, I wanted to switch to APFS.

Why not just retain the existing disk(s) and start a new ™ disk?

I think you're looking for => Mac OS Extended (Journaled, Encrypted): Uses the Mac format, requires a password, and encrypts the partition.

Not according to File system formats available in Disk Utility on Mac:

Looks like it's also possible to encrypt a volume directly from Finder (see below).