I spent a few weeks syncing my 75,000 photos with my OneDrive synced folder on the C:drive. I then imported all of my photos into Lightroom. I set Lightroom to save metadata to the actual photo files. The problem that I'm having is that every time I make a change in Lightroom, it seems to want to update all of my photos which then syncs all of the photos with OneDrive. This process is VERY slow and uses a lot of bandwidth which slows down everything else I need to do on the internet. I tried moving the catalog to a non-synced folder on my C:drive and that helped a little bit. It still takes about a day or two to sync with OneDrive every time I make a change to a photo in Lightroom.
In trying to fix the problem, I closed OneDrive and re-opened the OneDrive app. My files immediately showed as synced.
After it appeared that my files were synced I went back into Lightroom and added some tags to photos in just one folder. Now ALL of my photos (in all of my folders) are trying to sync to OneDrive again. It is now almost 24 hours later and OneDrive is saying that approx. 60,000 out of my 75,000 photos are remaining to be synced. Is Lightroom trying to save metadata to all of my files every time I exit? Even if it is, why is OneDrive so slow? I sure do hope someone can help me. I'm not sure if I should scrap Lightroom or scrap OneDrive. Or maybe my AT&T Uverse internet connection is too slow at 12mbps download and barely over 1mbps upload.
Saving metadata to file means, if the photos are Raw files in the maker's proprietary format, writing separate xmp sidecar files; and if they are DNG Raws or rendered RGB files (jpgs, for instance) embedding the xmps inside the files. Why do you need them? They are primarily useful if you plan to later do additional editing in other Adobe software - i.e. Photoshop. All 75,000? All that same metadata, and more, is already saved in the Lightroom catalog database - *.lrcat. For security purposes it should be enough to regularly backup the catalog to another drive or location (I backup the catalog to Google Drive) and of course to have backups of the photo originals. If and when you really need an xmp, create it on an individual basis with Ctrl+S.