[pfranz]

Personally, I have a network Time Machine backup and use Backblaze. I also keep a USB drive handy and clone a bootable backup via SuperDuper periodically--especially before large changes like an OS update. I've had to dig into the nitty gritty of Time Machine every year or so (usually stuff I do, but in any case failed backups are concerning).

Relevant to you, earlier this year (using Catalina) I swapped computers. My usual process is to create a disk image (usually with Disk Utility or SuperDuper) of my old computer and these overlay systems are tripping me up.

I remember my first attempt only looked to clone the OS / root system--not my user data files. I can't remember exactly what I did next, maybe clone to USB drive then create an image of that? But I pulled it up the other day and the disk image size covered my whole hard drive, but when I mounted it I just saw the root system (I thought I lost all my backup data). Using DaisyDisk I saw a lot of "hidden space." I noticed Disk Utility mounted two disks; Macintosh HD and Macintosh HD - Data, but Finder only showed the first on the desktop/sidebar and I had to hunt for the second under /Volumes/.

For simplicity I'm going to create a new disk image and pull out the relevant data. I never really had a need for a bootable backup on the network. I just figured I'd backup OS files in case I needed to pull up some oddball system hack I had on an old system.