This works as long as you have enough storage locally. Our photo library is ~3TB split over 2 users, and while you could theoretically use an external SSD for storage, that kinda cuts down on mobility. You could leave the drive attached and drag it around, or detach it and lose access to your photos on the go.

For a long time, I had a Mac mini running 24/7, where each user was logged in (via Remote Desktop), and that would synchronize photos to an external drive, and the Mac would then make backups (via Arq) to my NAS as well as a remote location.

I don’t count the Mac copy in my 3-2-1 as it is basically sync (each side, iCloud and Mac, are sync), and without versioning, ie APFS snapshots, if one side goes bad, so does the other.

I’ve since switched to using Parachute for day to day backups, and every ~6 months I make a manual full export of the photo library in case Parachute missed something.

I thought about going this route, but I have 73GB of photos currently, which will only continue to grow over time.

While not the biggest library, it’s approaching the point where I’d need to start buying upgraded storage on any new Mac I buy, or use external storage for my Photos library. One of the things I like about iCloud Photos is my computer doesn’t need much local storage, Photos will manage it, downloading full res images on demand and purging them as needed.

I’d want a backup solution that is optimized for this, to allow for backups of the originals, without having to have them all downloaded all the time.

Makes sense. Unfortunately closest thing I’ve seen is https://github.com/boredazfcuk/docker-icloudpd but that requires turning off Advanced Data Protection which is a nonstarter for me

A large library becomes hard to manage.

The family one is somewhere around 759gb. Having this stored locally fills a decent size drive so it needs to be on network storage. Macs don’t love doing this, and somehow it’s difficult to keep a file share mounted 100% of the time on macOS (though it’s 100% reliable on an Ubuntu vm hosted on that same mac).

I concocted a vile script to download iCloud Photos and then save them to a Synology.

I’m looking hard at UGreen or Ubiquiti do my next NAS. The Synology thing where you can put same or larger drives in the array is probably the only bit I’d miss at this point.

Can’t say anything about UGREEN, but UNAS with Unifi identity endpoint is magic on a Mac. You install it, sign in with your UI credentials, and it automatically mounts all shares you have access to whenever you’re on a network where the NAS is reachable.

It works on my LAN, but also over my site to site VPN from my summerhouse, as well as my road warrior wireguard VPN.