Can't move Photo Library to external SSD
This is about a Mac Mini A1347, if I remember correctly. Made maybe about 2012.
I know someone who has a 612 GB Photo Library. Currently it is saved on her Mac Mini which has a 1 TB internal SSD. Occasionally her Mac tells her the drive is getting full and won't let her download more pics from her phone. So, we thought we could move the library to an external drive to free up space on the internal SSD and she could work with the library on the external drive. We tried to move it to a 1 TB Samsung external SSD but it wouldn't move or copy. After waiting a few minutes watching macOS say it is preparing to move/copy the file we get a message telling us the external drive isn't big enough even though it clearly is big enough. I Googled some stuff about it. I tried reformatting the drive from exFAT to APFS, still we couldn't move the library. We had a small (megabytes) test library file which contained no pics and we were able to move it to a different drive formatted as exFAT with no trouble. However, for some reason we can't move the 612 GB Photo Library. Is there a solution for this issue?
Alternatively we discussed upgrading the Mac Mini's SSD from 1 TB to 4 TB. She takes a lot of photos. In the Windows world you can just clone the smaller drive's contents to the larger drive, install the larger drive and you're good. Is that doable with a Mac? Or do I need to do a full backup of the OS installation as it is on the smaller drive and restore it to the larger drive after installing macOS on the larger drive?
iMac 27″, OS X 10.11