The way Chrome OS “Files” app displays external storage devices with multiple partitions is a bit confusing at the moment. To quote this bug report:
The current external drive UI does not allow the user to intuitively recognize which partitions belong to which physical external device. Partitions of external media have the same visual appearance and actions (i.e. eject) as physical devices, which can lead to confusion.
The Chrome OS team is working on a solution for this problem. A recent code commit submitted to the Chromium OS repository talks about adding a partition icon for, well, partitions and a USB icon for the root folder.
I could not get my hands on these icons. However, the same bug report that I mentioned above, talks about how they are going to fix this confusion.
The bug tracks the work on partition grouping. Partitions which belong to the same external media device are to display as children under the common device in the directory tree UI. Eject button on root ejects all child partitions.
As I usually say about these code commits, this may or may not make it to Chrome OS. If it does, we should see this in the Canary channel first, in a few weeks or so from now.
Stay tuned to Chrome Story for more Chrome OS news!