We do not recommend storing the Photos App onto the JetDrive Lite.
You may have successfully transferred photos using iPhoto before. However, the new Photos application is slightly different from iPhotos, which may cause problems if one were to move Photos to the JDL. For safer data transfer, we recommend using Image Capture.
If you’re transferring from an iPhone to a Mac device, please try hitting the Command key + Space bar to open the spotlight search tool. Type Image Capture, launch Image Capture, and then try importing the photos into Image Capture before dragging them onto the JDL.
Please contact Apple for more help regarding Photos setup and operation.