External drive mounts as internal drive

I thought I’d start a new topic with this since it appears not to be a permissions issue. I thought I had solved previous problem by attaching the problem drive to a different Mac, erasing, renaming, reformatting, and copying the files back to it. But no.

On my MacBook Air, the SSD external mounts correctly, as an external drive. And it mounts as external drive when attached directly to one of the iMac’s USB ports. If I attach it to my external OWC Thunderbolt dock, attached to iMac, it mounts as an INTERNAL drive. I have three other external drives attached to that same dock, also via USB, individually, not daisy-chained, and they all mount correctly as externals. They all are regular drives, not SSD. I can live with this, grumpily, but am fascinated. When attached to another OWC thunderbolt drive connected to the Air, it mounts correctly as external. Both Macs on latest High Sierra. What gives?

I have no idea if this is related, but IIRC Thunderbolt technically connects to your Mac’s chipset through PCIe. PCIe is generally used as a bus for internal slots and there are SSD PCIe cards. Such memory would be considered “an internal drive”. Of course this wouldn’t explain why your Mac couldn’t see the drive as a USB device (it most likely can) or why other USB disks attached to that same TB dock show up fine as external. PCIe might the hardware bus, but the protocol used for communication to/from your USB SSD is still USB. Does your System Profiler (Hardware > Storage) confirm that?

I wonder if this might be an artifact of the OWC dock and/or the driver (kext). On my Elgato TB2 dock I have never seen an external USB drive show up as an internal drive. I have, however, seen the TM disk show up as a generic external USB drive (which it is) instead of with its TM icon from time to time. Possibly in your case, the icon display is simply wonky (macOS bug? like my TM icon) while actually, your Mac sees the SSD drive just fine as external USB media connected through TB.

I am totally confused. First image(SSD-Dock1) shows Disk Utility with the SSD attached to dock, and second image (SSD-Dock2) shows system report of that connection. Third image (SSD-iMac-USB) shows system report when SSD is attached directly to the iMac. I believe the OWC audio device is the audio connection on the dock. I am assuming the USB3.1 bus that shows up at the bottom is my second, unused, Thunderbolt 3 port on the iMac. I have also attached an image of the iMac Model info.

Other than it being odd, is there any reason I should be concerned that this is happening? This iMac had its internals, including processor I believe, replaced by Apple last year when it totally bricked.

I don’t think there is reason to be concerned. It’s just odd. If you go to profiler and check under Storage when the USB SSD is connected to your dock, what does it say for the protocol? It should say USB which would be consistent with the “connection” shown by DiskUtility in your screenshot. The “internal” is most likely just a misnomer.