How to clone a macOS Catalina drive

Until macOS 10.15 Catalina, Mac users knew: their startup volume was a single volume, just as it appeared! (Okay, for Fusion drive users, there are two physical drives managed by software to appear as a single “disk drive,” but that’s separate from the data organization that is a volume on a drive.)As I wrote a couple of months ago, Apple relies on a feature in APFS (Apple File System) called “volume group.” This allows macOS to link together two separate volumes t