I decided to give CCC a try and downloaded the trial version this morning. After selecting the Source and Destination disks, I got a cautionary dialogue box warning that the Destination disk (just erased twice with Disk Utilty) had remnants of APFS files that could cause future issues such as inability to boot, et cetera.

However, it seemed to me that a true copy should have the correct filing system and, if I erased to go back to the old filing system (not sure if that's even possible), a full restoration would be a problem. That is, I'd be restoring with something other than what I had.

Anyway, I disregarded the caution and have begun a backup with the disk as wiped by Disk Utilty. Once it's completed, the first thing I'll do is see if it boots.

Meanwhile, as the Subject line says: "Call me confused". We have some CCC users in FTM and I'd be interested in knowing what they did.

First, I'm not sure what you mean by that.

I ran into your dialog box once, and since I wasn't about to erase my entire SSD and then have to restore my four working partitions without a compelling reason I just went ahead as you've apparently done and experienced NO repercussions.

Okay.....good news. Thanks.

You got me thinking that I just erased a partition and didn't get that pop-up; do you remember if there was a "Don't ask me again" check box?

I meant....if my drive is APFS but the copy is not, and if I had to restore my drive, I be installing a filing system other than what I had. My assumption was that CCC meant it did not want to copy an APFS.

I don't recall.

By way of update....I have booted from the CCC disk, although it seemed to take quite a long time to get to my desktop complete with Dock. This response is using the clone disk.

More update....I rebooted with the backup disk powered down and the boot went much, much faster.

Going to be off-line for a while....Abby insisting on her first walk.

In my experience, the first time that you boot a CCC clone from a HDD takes a noticeable amount of time. The second time is much faster, so powering down your backup disk may have had nothing to do with it. The next time that you update the clone, the first boot will again be slow.

Booting a clone (even the first time) from an SSD is always fast.

Once your drive is formatted APFS the only way to get it back to HFS+ is by reformatting it, and hand in hand with that is if you restore to an APFS drive from an HFS+ drive you'll wind up with an APFS volume.

I don't think your assumption is correct, but I've got no idea what the CCC warning really is about.

As far. as I can tell CCC doesn't care what the format of the source and destination drive is. If you clone from APFS to HFS the clone is a bootable HFS volume and vice-versa. At least that is how it works for me.

I haven't tried cloning from an HFS volume to APFS, but cloning an APFS volume produces an HFS volume for me.

I probably should have added CCCing form APFS to APFS produces a bootable APFS clone volume. In other words the resulting clone will have whatever disk format the TARGET drive had before cloning. CCC does NOT format or reformat either the SOURCE or TARGET drive, it merely duplicates (clones) the CONTENTS of the SOURCE drive onto the TARGET drive. The exception is when you clone to an image (sparse disk image) file which is a complete clone, but is unbootable.

The penny has dropped.

I think this is the last piece of the puzzle.