Transfer 6 TB from old to new XTHD (12TB) best way to keep folders connected to LRC and catalog?

It sounds like it would be a good idea to clarify with everyone you talk to what exactly they mean by “cloning,” because people seem to be using different definitions of it. 

The way I have understood the term “cloning” is simply taking the folder hierarchy and the files in it on volume A, and exactly copies that folder hierarchy and files to volume B. This understanding of “cloning” is not affected by the capacity of either volume; as long as volume B is the same capacity or larger it doesn’t matter. 

It sounds like you and I already use Carbon Copy Cloner, and that is exactly how it clones by default. 

So of course the next question to ask is, in what sense would cloning or copying not use the entire available capacity of the destination drive? There is one way that can be true: If you’re cloning and the destination is not a normal volume like a hard drive or solid state drive, but an image as the destination, not just a volume. (Often called a disk image, like the kind you can make with Apple Disk Utility, even though today’s volumes are often not actual disks any more.) A disk image typically has a fixed size because it’s really one big file that acts like a hardware volume; it can be mounted or unmounted. For example if you decided to clone 6TB of files to a disk image on a 12TB drive, you get an 6TB image file which is not useful to Lightroom Classic or any other software unless it’s mounted. 

Or maybe the Glyph tech was thinking of some copy method that would clone an entire partition/container along with that container’s size limit, or they were thinking of some file system with an 8TB limit. Either way, those are not concerns with a normal Mac volume clone. 

For this discussion — transferring files from an old 6TB hard drive to a new 12TB hard drive — the traditional and typical sense of “cloning” is that you’re just going to copy over the files. That’s it.

I see you said Carbon Copy Cloner is already doing its thing. That’s great, many of us have migrated using CCC; I have done that more than once as I had to get bigger drives over the years. (rsync is fine, but Carbon Copy Cloner is basically a point-and-click app that does the same thing. CCC might even use rsync under the hood.) When it’s done, you can simply reconnect the top level folder(s) on your fresh copy: As shown in the picture below, open the context menu* for each top-level folder, choose Update Folder Location, and point it to where that folder is on the new drive. Lightroom Classic will reconnect everything within that folder, including all subfolders. So if all photos are contained under a single top-level folder, then it will only be one step!

*If you’ve configured right-click on your Mac mouse, open the context menu with that. If not, Control-click to open the context menu, or use however you’ve configured secondary click on your trackpad, stylus, etc. 

Lightroom-Classic-Update-Folder-Location-parent.jpg

The excellent resource The Lightroom Queen also has a guide for this, because migration is so common:

How do I move Lightroom to a new computer?

If you change the new drive's name to exactly what used to be the old drive's name (and just clone the old drive exactly onto the new drive), you shouldn't have to re-connect anything. Don't go moving folders around within the hierarchy, or moving files around within the folder hierarchy, or renaming the folders or files. The only move is from one disk to another.

For anyone reading along with a Windows computer, there are no drive names, but drive letters, so make the letter of the new drive the same as the old drive used.