Some Notes on iCloud Photo Library on a Mac

by: léonie

Last modified: Oct 24, 2018 7:48 AM

6 4198 Last modified Oct 24, 2018 7:48 AM

iCloud Photo Library is a very convenient way to keep photo libraries in sync across several Macs. Most changes done on one Mac will update across all Macs that are also using iCloud Photo Library (let's ignore the iOS devices for now).

Exceptions to the rule: Use Photos and iCloud Photo Library on multiple Mac computers - Apple Support

Projects do not sync: Books, Calendars, Cards, Slideshows
Faces thumbnails do not sync, only searchable faces tags (in Photos 1 and 2). In Photos 3 on High Sierra and Photos 4.0 the People album will sync between devices.
Referenced photos do not upload to iCloud Photo Library at all.

A Photos Library needs to be on a volume formatted MacOS Extended (Journaled) or APFS, if you want to use iCloud Photo Library. https://help.apple.com/photos/mac/1.0/?lang=en#/pht211de786Not all media items can upload to iCloud Photo Library. If the Photos Library has been migrated from iPhoto or Aperture, it can contain media, that are incompatible with iCloud Photo Library, for example some audio file formats or high resolution TIFF images. These will show as items "Local only" at the bottom of the Photos view.Because the iCloud version of your Photos Library may be missing items compared to the local version, restoring a Photos Library from iCloud can be lossy. Always keep a good local backup.Occasionally Photos will start to upload the complete library again to iCloud to compare it to the iCloud version. This new upload may take a very long time. For example, my library with 36000 photos needed a full week to upload again. A new upload will happen after the following events:

If iCloud Photo Library is turned off and on again for a library.
If the Photos Library is moved to a different drive.
If the Photos Library is restored from a backup.
If the Photos Library is repaired; see the footnote in: "Fix missing or incorrect thumbnails in Photos - Apple Support"

Try to avoid these situations, if possible. Repeated crashes of Photos can cause a repair of the library, but also permission issues, when using the Photos Library from different user accounts or over a network.

Avoid switching the system photo library, because it will disable iCloud Photo Library.

Avoid turning iCloud on in Aperture or iPhoto, because only one library can sync with iCloud Photo Library and enabling iCloud for a different library will disable it for your current library and cause the upload again.