Yesterday, I took my 2015 Macbook Pro running OSX 10.13.6 and backed it up using Time Machine to an external hard drive. I then immediately updated my laptop to 10.15.4. I plugged in my external hard drive to do back it up again using Time Machine, and the subsequent backup was over 70GB(!). Looking at About This Mac -> Storage, I currently have an 256GB SSD, with 84GB of Photos, 78GB of documents, 18GB of Music, 7GB of Apps, 11GB of System, 16GB of other.
I can not figure out why this backup was so enormous. What did Apple change so significantly over the past two operating system iterations? I know they dropped 32bit support for applications from 10.13 -> 10.14. Could this be why this backup to be so large?
My cloud backup service (SpiderOak One), also decided that it needed to backup 40GB of stuff. It looks like its doing mostly photos in Photos Library.photoslibrary/originals, but likewise I don't see why it would need to do this. I have it running constantly and I believe it was working and up to date prior to this backup.
I believe that these two issues are related. Perhaps Apple changed its file system yet again (like from 10.12 -> 10.13, where it changed to AFS)? Maybe it changed how it handles Photos?
Question: 1. Why was my Time Machine and SpiderOak backups so large? The only thing I did was update my operating system.