Photos: One Giant Library vs. Multiple Large Library files

There is no right answer to this. Theoretically, Photos has no upper limit on number of items, but there is an undeniable hit on performance as you reach very large numbers. It Is slow to process the items, slow to launch, slow to close. I certainly would not try a single library with more than 100k images on a Mac with only 4 gigs of Ram, for instance. But how gigs is enough? For how many images? I've no idea.

The protection against corruption is a rigorous back up schedule to external hard drives.

This gentleman manages 2+ million images in Mylio, but he uses a macPro.

www.naturalexposures.com/corkboard

Please forgive me for jumping in here folks. I just wanted to comment on one part of the action plan outlined yesterday:

• Merge in the next library once Photos has pushed originals to iCloud and freed up enough space on the MBP's drive.

I'm not sure we know enough about the inner workings of the optimization process to say that it will be triggered in a timely manner by the merge process you describe, unless you are actually creating a storage shortage that is both detectable and survivable. (If the Mac mini drive has lots of free storage, optimization may never be triggered. On the other hand, if it does not have enough free storage for the next library merge, will there be a race between the optimization and the merge, will the next merge be refused, or will it be attempted and fail? I hope that at least the last is not likely.)

sjsherratt wrote: … (Richard, you mentioned "Clean Up" - I'm not familiar with that).

From Jackson Square in New Orleans-- Is he juggling 2 or 3?

Clean Up lets you remove items. It's new in macOS 15 Sequoia. It certainly won't work in Catalina, but it's possible the information will be there-- it's in iCloud. But somehow I doubt it.

I keep multiple Libraries just because I find it easier to manage. One difference from you is that my "System Library," the one that gets used for new iPhone pictures and for connection to iCloud Photos, is a Favorites Library.

I find the best pictures from over many years, and I add those to the Favorites Library where I can see them on my iPad and show them to friends and family. I have a Library for work pictures, and I have Libraries for my wife's old family pictures and for my own family's old pictures. (I kept getting mixed up about just which family "Great Aunt Edith" was in, so I split up the families.) I have a Library for iPics-- all the pictures from my (and others') phones and iPads. I have scans from old slides from the days of film. I have a Nikon Library for pictures that I take with my serious camera, and that's where I spiff them up, rate them, and choose the best. Every picture in my Favorites Library is also in another Library. Favorites has about 17 000 pictures.

I don't want pictures to never show up just because they're old. I like seeing my favorite pictures from all ages on my iPad, on my iPhone, and at iCloud, com. I use  PowerPhotos ($30) to copy pictures between Libraries.

I use "Download Originals" on both my Mac and my iPad, but I use "Optimize" on my iPhone. I backup my computer with Time Machine, and I make entire copies of my Libraries monthly. (If I remember…) Backups don't work if "Optimize" is chosen, since I'd just be backing up reduced files.

Libraries can get corrupted in lots of ways, especially from ailing drives and crazy "mac cleaning" apps. But the version at iCloud is safe from all that. However, iCloud isn't much of a backup, so serious backups require extra external drives.

sjsherratt wrote: … keep all of the original images on the Mac mini and use the Mac mini as the source for serious backups. I am not sure if I will run into problems since the Mac mini doesn't support MacOS beyond Catalina and all of my other devices run the latest OS.

iCloud is the only way to have exact copies of Photos over different OSs. But I'm not sure what happens if you look at images on an older OS that were modified with "Clean Up" on a Sequoia machine, since Clean Up doesn't exist before macOS 15. I have an older MacAir running Sonoma-- I'll have to check. Or, I guess you can check that, as well.

Using a Catalina machine for backup will work if you temporarily plug the external drive into the MacBook and drag the Library over to it, and then plug back into the older machine-- and don't attempt to run that Library. Older Photos can't open a newer version library.

Keeping a Photos Library on external storage for a MacBook is problematic, since it would probably be plugged and unplugged, messing with background processes. I keep most non-Photos stuff on a small portable external drive so that I can keep the Photos Library on the internal drive.

sjsherratt wrote:… I am mostly interested in preserving the originals.

I've spent hours taking off dirt and decay from century old pictures, as well as in restoring some deteriorated slides and prints-- I'm wondering if Clean Up could have saved some time. I haven't done much with it, yet.