Is there a quicker way to pause Photos uploading to iCloud?
From playing about with opensnoop, what seems to happen when you click "Pause" is that Photos (by way of cloudphotosd) adds something like the following two lines to a file within your photo library called private/com.apple.cloudphotosd/CloudSync.noindex/State.plist

&lt;key&gt;pausedUntilDate&lt;/key&gt;
&lt;date&gt;2015-04-30T23:57:01Z&lt;/date&gt;


However just editing that file doesn't seem to be enough, because it also seems to do something with some other binary files, for example private/com.apple.cloudphotosd/CloudSync.noindex/Engine/statistics.bin. But given that they appear to be in a binary format it's a little bit more difficult trying to work out what Photos is doing.

Here is the full trace from me running opensnoop while clicking Pause in Photos' preferences window. Maybe someone else can fill out the rest of the picture.

  501    395 cloudphotosd  45 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex/Engine/statistics.bin 
  501    273 Finder        36 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex/Engine 
  501    273 Finder        36 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex/Engine/statistics.bin 
  501    273 Finder        36 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex 
  501    273 Finder        36 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex/State.plist 
  501    273 Finder        36 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex/State.plist 
  501    273 Finder        36 ~/Pictures/Photos Library.photoslibrary/private/com.apple.cloudphotosd/CloudSync.noindex/syncstatus.plist