Efficient Workflow for Backing Up Photos to iCloud While Using Lightroom

This might be doable. Since you’re asking about backing up to iCloud, that’s much easier than when people ask how to work directly off of iCloud which is a lot riskier.

It is true that the folder organization in the built-in copy feature in Lightroom Classic is not useful for a backup that can easily be restored and relinked to a catalog. Although I haven’t done photo backup to iCloud Drive, if I did, my approach would be similar to what JohanElzenga suggested: Use backup software to automatically maintain an exact copy (a backup) of your existing photo folders, but inside the iCloud Drive folder. iCloud Drive would upload that duplicate folder structure to iCloud.

But don’t start before thinking through the potential issues below.

More specifically:

1. Choose a good, reliable Mac backup application. For a volume-to-iCloud Drive backup, Apple Time Machine won’t work, so you’ll have to use something like Carbon Copy Cloner, Chronosync, or Hazel; all are well-established and trusted, and all support incremental backups so that only the photos and folders that change are updated on the destination. (Although Hazel is not strictly backup software, one of its automatic housekeeping features is to keep a folder’s contents the same as a folder on another local volume.) All are paid commercial software.

2. Set up the backup software to make an exact copy of your photo volume to a destination folder in iCloud Drive, and also set up its scheduler to automatically update the destination folder on its own, like daily or hourly. These apps will maintain the structure of the subfolders within the parent folder.

Johan asked a good question about whether iCloud has an “online only” option. This part is still confusing to me. I believe this option is Optimize Mac Storage in System Settings / userID / iCloud.

Note: It’s possible that I don’t have a complete understanding about everything in the following paragraphs. If you want to try and confirm how it works yourself, here’s an Apple description of iCloud Drive options, and also two more technical analyses by Howard Oakley:

Store files in iCloud Drive on Mac (scroll down to “Store older documents in iCloud when space is needed” which covers Optimize Mac Storage)

How iCloud Drive works in macOS Sonoma

iCloud Drive in Sonoma: Optimise Mac Storage or not?

If I understand iCloud Drive correctly, when you copy some files into iCloud Drive, they are first copied to a local folder on your Mac (path below) and then queued for upload. This means you may see a temporary drop in free storage space on your startup volume as iCloud Drive works through the upload queue of the contents of the external drive. In other words, I don’t think a file is directly uploaded from its current location.

The actual local location of the “iCloud Drive” folder you see on the macOS desktop is:

~/Library/Mobile Documents/com~apple~CloudDocs

(within the user account Home on the startup volume)

• If Optimize Mac Storage is off (the default), I think that location works as a sync folder: The files exist on your Mac (if room) and on iCloud Drive, and iCloud Drive keeps the local and cloud copies in sync.
• If Optimize Mac Storage is on, that location works as an upload folder, so after iCloud Drive uploads what’s in it, a “dataless” placeholder is left behind (see second link above) so that you can still see the structure of iCloud Drive files without them taking up any space on your Mac startup volume.

Because of the intricacies of how iCloud Drive works depending on its settings, before jumping into this, it’s strongly recommended that you test your backup system with small but sizable folders of expendable test files to see if you understand how it’s actually working, and (important) whether the local backup/sync software you pick works properly with iCloud Drive dataless placeholder files.

And, of course, as every IT person will say, you must test recovery from backup to make sure you are confident that restoration would be reliable if the external drive of originals fails.

If after testing you decide you are comfortable with and confident in how the local backup software and iCloud Drive work together, without unexpected side effects, then you can go ahead with this plan.

At the top of the right hand panels in Lightroom Classic (LrC) there is a option to save to an additional location. Check to see if iCloud drive shows up there. At this point, is where you take care to create the same file naming and folder structure that you use on your local drive.

Remember, LrC's data is kept in the Catalog file. The photos are not in that Catalog file, they are in their own separate folders (and even separate drives if you set it up that way). Both the catalog and photo files need to be backed up.

When you create derivitive files, exported .jpgs for for example you will need to come up with a way to get those into iCloud if you want them to be there.