Photos library size difference [Apple Support can't help]

[KevHudThom]

I was escalated to third tier of Apple Support and they can't answer this question or help me:
I'm trying to migrate my Photos library from an Old iMac from early 2015 to a New iMac just purchased Sept 2020. Both are running Catalina 10.15.7
When I look at the Old iMac storage, it shows 1.29 TB available of 3.12 TB total -- that is, 1.83 TB used. If I click on "Manage..." it shows that Photos is taking up 1.13 TB.
However, when I look in the Pictures folder, my Photos Library shows as 2.31 TB. Also, when I considered using Migration Assistant, it showed my documents and data totaling about 2.7 TB.
I don't want to copy over a 2.31 TB file to the New iMac if the Photos library (which includes videos) is *really* 1.13 TB.
What's going on here?

 

[mlblacy]

I wouldn't worry too much. There are a lot of variables that would cause the library to appear to be different sizes. If you are copying to a different size hard drive, that could make a big difference in the library size. Also, you may have a lot of garbage/previews in your original copy (if it functions much like Aperture did).

I have just about finished moving my Aperture3 image library into Photos, and into a new computer. My main library was around the same size at 2.3TB, which had gotten to the point where both Time Machine and the Vault would barely function. Doing a finder copy to a new drive could take 3-5 days, and the results were a bit shaky. Carbon Copy Cloner is nothing short of amazing, and I could do a clean copy in 8-12 hours (not days). Incremental backups take minutes, not hours (even to a USB drive). When your image libraries start to get that size, you are better off keeping them on external drives. I use a Thunderbolt3 drive for the libraries, and then backup to another external drive (USB is fast enough for a backup drive). You can set up task shortcuts in CCC for each library, or drive you are copying to.

The point is, I would use CCC for the copying. You can download a 30 day demo too. PS: tech support for Photos is almost non-existent.

 

[wilberforce]

The photoslibrary file contains more than just the original photos. It also contains renders, previews, object recognition, metadata, etc. Right click on the file in Finder to show package contents and you can get an idea of what it contains.
Also, in Storage, "used" does not necessarily equal "total" minus "available." It can be "using" storage for caches etc but this storage can be released and therefore is also "available."

 

[KevHudThom]

Interesting, thank you.
Within "show package contents" there is a folder of 1.14 TB called "originals" with a bunch of subfolders containing mostly jpeg and mov files. And there is another folder of 1.16 TB called "resources" and inside that, if you drill down through cpl>cloud sync.noindex>storage>filecache there are a bunch of folders containing mostly jpeg and mov files.