Why is iCloud uploading my entire iCloud Photo library again after I moved its location?
That is unfortunately what will happen, when you move a Photos library to a different drive. You have to enable iCloud Photo Library again for the moved library, and iCloud will upload all photos again to merge them into the library in iCloud. There are many reasons for iCloud to upload the library again and to merge it again with iCloud:
- When you move the library to a different drive.
- When you restore the library from a backup.
- When you temporarily toggle iCloud Photo Library off and on again
- When you switch the iCloud library temporarily to a different library and back to your original library.
- When you enable My Photo Stream for a different library, for example an Aperture library and then switch back.
- When you repair your current iCloud Library.
All these events will cause Photos to upload the library again to iCloud and to compare it to the current iCloud Photo Library in iCloud.
You may not be able to enable iCloud Photo Library again, if your library is very large and you do not have much free cloud storage. Then see this user tip:
If your Photos Library is large, be prepared for a long upload time if you repair your Photos Library, change its location, or disable iCloud Photo Library. Sometimes there is no help for it, but uploading the library again may take a week or longer, depending on the size of your library.
Apple is confirming that repairing the library will result in uploading it again in this document (Fix missing or incorrect thumbnails in Photos - Apple Support).
Update: 🙂 Apple changed the wording from "re-uploading" to "re-updating" in this newer document:
:How to use the Photos library repair tool - Apple Support
If you repair a library that's automatically updated with iCloud Photo Library, the entire contents of the library re-updates with iCloud after the repair process completes.
But whether it is "updating" or uploading, be prepared for a long wait after repairing your library.