Partition Viewable in Disk Utility but not Finder

[theorist9]

I have a 5 TB Seagate Backup Plus external HDD that was formatted in HFS+ (GUID Partition Map) using a 2014 MBP; the drive was purchased in 2015, so this was probably done while running Yosemite. The MBP is currently running High Sierra. The drive has three partitions: A bootable backup made with Carbon Copy Cloner, Time Machine, and "just some files in folders" (let's call that "Folders"). When I attach that drive to my 2014 MBP, I can see and access all three partitions in Finder.

However, I'd like to copy over the contents of the "Folders" partition to my 2019 iMac. When I attach the drive to that machine, I can see all three partitions in Disk Utility, and can mount and unmount each. However, the Folders partition doesn't show up in Finder. I've tried rebooting the machine, unmounting and remounting the drive, etc., and nothing works. I also did First Aid on the Folders partition, and got no errors.

There are workarounds--I could copy the contents of the Folders partition onto another external drive, and effect the transfer that way. But I'm just curious why this might be happening.

Yeah, the drive is seven years old (that's part of why I'm offloading stuff from it), but the behavior still seems curious.

 

[Fishrrman]

When a drive is acting flaky, the FIRST ORDER OF BUSINESS is to "get stuff OFF OF that drive" and onto a known good one.

So that's what I'd be doing before I worried about anything else...

 

[NoBoMac]

Got to ask, to get it out of the way: Finder Preferences correct for the sidebar on the 2019 machine?

Seeing the icons for the drive/volumes on the desktop?

 

[theorist9]

Got to ask, to get it out of the way: Finder Preferences correct for the sidebar on the 2019 machine?

Seeing the icons for the drive/volumes on the desktop?

Ha! I didn't think to check that, because I was seeing both of the other partitions on the drive, so I assumed everything was fine there. But when I did check, I noticed that "External Disks" was neither checked nor unchecked. Instead, it had a blue box with a horizontal white line instead of a checkmark (indicating some partitions but not all had been selected for viewing). When I clicked on it to change it to a checkmark, then the third partition appeared.

I've seen that behavior in iTunes (it's what it shows when you've selected some chapters of an audiobook but not the whole thing)--but never in Finder; there, I've only seen all or nothing.

Thanks!