What are the essential folders in Photos Library.photoslibrary to back up? 90% of the data is original photos, but the other 10% changes a lot. For an almost 2Tb Photos libray this amounts to a lot of storage if the entire library is considered to have changed as a result of changes in the 10%.
Frequent incremental backups of the entire library are also too time consuming and costly if one uses cloud backup services. Often the original image files do not change, and it’s only sqlite or other database files that trigger an incremental backup.
I want to be sure I am backing up every original file, but I am less concerned about those I could regenerate (e.g. the face database) that also change frequently. I also want to retain the exif data and the file numbering from my camera. This last use to be captured in the file names in the masters/originals folder, but at some point Photos start using UUIDs for file names and now the UUID/numbering link is in a database. Since I want to retain those links I may need to include some database files in the backup.
Here is an example of a file that may be redundant and can be skipped:
Photos Library.photoslibrary/resources/renders/F/FB170E5B-AAAA-4B81-A0DE-CD59AF_1_201_a.jpeg
because it is scaled down version of this original:
Photos Library.photoslibrary/originals/F/FB170E5B-AAAA-4B81-A0DE-CD59AF.jpeg
