Hard Links and Photos for OS X
February 11th, 2015
Jason Snell, after reviewing the beta of Photos for OS X, has figured out how Apple imports photos into the new Photos for OS X without taking up any additional space:
It creates hard links to the contents of your iPhoto library inside the Photos library. If you delete your iPhoto library, the files that were hard-linked from the Photos library still exist in the Photos library and aren’t deleted.
This is really great.