How can I copy RAW photos with metadata from Mac Photos app to an external hard drive?
Use the Disk Utility application to create a sparse bundle on you external drive. You can then mount this as a Mac OS Extended (Journaled) volume for storage of your RAW photos. The metadata will then stay with your RAW photos. If needed, you can even use the Disk Utility application to increase or decrease the size of the sparse bundle image.

Instructions to create the sparse bundle are as follows.


Open the Disk Utility application.
From the menu bar, select File-&gt;New Image-&gt;Blank Image....
Input your requirements in the window. Below is an example. The size is the maximum size that the sparse bundle can grow to be. Initially, this example sparse bundle only takes 247.1 MB of space on the external MS-DOS (FAT) formatted volume named MYFAT.
Select the Save button.


  Note: A sparse bundle is a folder containing many small files.





Instructions to resize the sparse bundle are as follows.


  Note: You will need to eject the sparse bundle before resizing.



Open the Disk Utility application.
From the menu bar, select Images-&gt;Resize...
Select the sparse bundle folder. I my case this would be named My RAW Pics.sparsebundle.
Enter a new size. In my case, I chose to double the maximum size to 200 GB, as shown below.
Select the Resize button.




A final note regarding the use of other image files.

You can also create a image as a dmg file. The difference here is that volume size is limited by the maximum file size of the format used by your external drive. Also, dmg file occupies space on your external drive equal to the size of the stored Mac OS Extended (Journaled) volume. A sparse bundle grows to occupy space on the external drive as needed.

You can also create a sparse image file. Like a dmg file, a sparse image file volume size is limited by the maximum file size of the format used by your external drive. Like a sparse bundle, a sparse image grows to occupy space on the external drive as needed. Again, a sparse file image is a single file, where as a sparse bundle image is a folder containing many small files.