I wish to move my Photos Library to a secondary drive, both formatted with APFS. I still have the iPhotos Library from where the pictures were imported.

I'm concerned that when moving the Photos and the iPhotos libraries to a new drive the shared masters will be duplicated and increase storage usage.

Is there a way I can move both libraries and preserve the link between them?

  • 1
    This may depend on whether you're on HFS+ or APFS. APFS doesn't have hard links. I honestly don't know the answer, but see eclecticlight.co/2019/01/05/… and superuser.com/questions/33268/…
    – Tetsujin
    Commented Aug 30, 2019 at 6:15
  • @Tetsujin Both drives use APFS. How does Photos link its masters to iPhotos library on APFS?
    – lpacheco
    Commented Aug 30, 2019 at 10:09
  • If the links have survived at all, they will be copy on write clones. Note that the two folders do start to differ from the moment they are created, & iPhotos won't open in Mojave so I'm not really sure what purpose it would still serve, tbh. I dumped mine years ago, Aperture too:\ so I can't test at all.
    – Tetsujin
    Commented Aug 30, 2019 at 10:16
  • There was some error on some update of iPhotos or Photos and some of my old videos don't work in the Photos library. I've found that the library still has the original files in working condition and I've been re-importing them, but I'm unsure of discarding my Photos library before I finish and for some time after.
    – lpacheco
    Commented Aug 30, 2019 at 11:01

1 Answer 1


So, no definitive answer.

I had copied my iPhotos, Aperture and Photos libraries to the new drive using Finder, but I was worried I was using unnecessary space. I did a new copy using rsync as follows:

rsync -azH --progress Aperture\ Library.migratedaplibrary iPhoto\ Library.migratedphotolibrary Photos\ Library\ \(Aperture\).photoslibrary Photos\ Library\ \(iPhoto\).photoslibrary /Volumes/Secondary\ SSHD/Users/me/Pictures

Now I'm sure I'm using too much space. :-)

This command should preserve hard links from the source in the destination, but as @Tetsujin commented on the question APFS doesn't support hard links and I don't think it would use copy on write with files in different media (what would happen if I ejected the media?).

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