Situation. Library 2014 initially indicated as “system library”. Created second library 2015. Wanted to see what happened when I loaded it to the cloud by re designating 2015 as the system library. It uploaded itself, just fine, but is now proceeding too download my original full size RAW 2014 library into 2015. Disk volume problem obviously so have paused things. If and when I let this re download complete, is my old 2014 library fully duplicated and can it be deleted. Is this a way to merge (very slowly) multiple Photos libraries? Basic observation. You can have only one library in the cloud. You cannot easily merge libraries (I read, and know about FatCat option). The designated system library on the cloud is limited to 200 Gb free, with non-competitive pricing over that. Have a time machine so can easily start over. This question must have been asked before, but I can’t find out if zi can delete the old 2014 initial system library safely. Is everything really duplicated by the wasteful full size download. It would appear to me that the single system library, 200GB limit, and inability to merge old libraries before using the iCloud is an invitation to Lightroom.