Robert Paris wrote:… So what are you saying about "run them from there"???? Are you saying I could plug them in to my main computer, a 2021 MacBook Pro (Sequoia 15.6.1), … and just what (?), double click that huge library file???
It doesn't matter where the Photos Library is (with some restrictions,) when you double click on it, Photos opens it. Many people keep their Libraries on external drives. The restrictions are that the volume must be properly formatted and local-- that is, not on iCloud Drive or on a NAS or on any other networked type setup. With newer SSDs with nearly 1000 MB/s transfer speeds over USBc, you can't see much difference. Also, Spotlight searches from the Mac won't penetrate the Library database, and there are some funny things with location lookup, but that's all.
I use Time Machine to do daily incremental backups, recording only the changes that have occurred since the last backup. It's fast, but it does mean that a Photos Library needs to go through a TM Restore process to put it all back together. I also do monthly (more or less) direct copies of the Libraries to another drive, and I keep the last few months. So I rely on multiple backups. Because I use a MacBook, I don't want a drive hanging from my port as I move around, so I keep my "Favorites" Library on my internal drive, and I keep lots of other stuff on a small one ounce SSD that I carry with me.
And regarding your last question, I went into photos on my iPad, clicked on the user icon in the upper right corner but I do NOT see anything that says "From My Mac"... Tell me where I might look for that???
"From My Mac" would be an album. Some transfer methods send pictures from a computer to the iPad/iPhone in a way that doesn't give Photos full control. Photos can show those pictures, but can't do much else-- Photos can't even trash the "From My Mac" pictures-- it must all be done from the computer. I don't have "From My Mac," but I think I did some time ago. I thought it was weird. Those pictures also won't transfer to iCloud.
… If it's just from the iPad which I'm guessing is the answer then I would ask and what is going to put them back on there???
You've got backups, and that alone should give you confidence. The Mac should be the main hub for you. It's way easier to work with pictures, edit, crop, type captions, use albums and folders, on a Mac than on a mobile device. iCloud Photos is a synchronization service. When you engage iCloud Photos on a device, then the Library on that device is kept exactly the same as the iCloud Photos Library. So, for instance, if you take a picture with your iPhone, it is added to the iPhone's Photos Library, copied to iCloud Photos Library, and then copied to the Photos Library on each of the other devices that you have connected. If you delete a picture on your Mac, then that picture is deleted at iCloud and on all the other devices.
So, if you have your Mac connected to iCloud Photos, then all the pictures in your Mac's Library are also in the iCloud Photos Library with all the metadata, edits, comments, etc. You can go to iCloud.com and convince yourself that this is so. When you turn on iCloud on the iPad, Photos will make sure that all of the pictures at iCloud.com are transferred to the iPad. It could take awhile. My "Favorites" Library has about 150GB, and it might take a week for a full transfer.
Keep in mind that iCloud is designed primarily for mobile devices, and since syncing uses the battery, and since lots of people are very anxious about battery drain, the iPhone and iPad will avoid syncing when not plugged in. And since syncing uses processing power, and people hate slow-downs, iThings will avoid syncing while you use them. And since syncing requires bandwidth, the iPhone and iPad will avoid syncing when the internet connection is weak.
So, if you want faster syncing, then find good wifi, plug the phone in, and leave it alone. All this applies to a lesser extent for the Mac.
