virtualbox.org

[quote="spbarrett"So the issue appears that the host OS passes the mounted file system directly onto guest OS.[/quote]
Yes. I thought that was obvious, but perhaps not It's not called "USB pass-through" for nothing, the guest OS sees the actual device with whatever is on it. The pass-through works on a much lower level than a filesystem.

Upon export the VDI format converts to VMDK so compact no longer works.

I'm honestly unsure if compressed VMDK can support split files at all. I know VirtualBox does not. For regular files, split VMDK (chopped up into 2GB-sized chunks) is an option, and it was invented exactly to work around the file size limitation.

If anyone knows of a single file system format that is supported under Solaris 11, Windows 7-10, and Linux 6 & 7. I'd like to hear from you. I have tried everything but am still haven't discovered any that are "supported".

That's something VirtualBox can't really help with, you need to talk to the Solaris guys. As far as I know, FAT32 is really the only FS supported more or less everywhere, but it has serious limitations. ExFAT is supported on most newer OS releases but not Solaris 11.

At present I don't think there's any file system that supports 4GB+ files and works across Windows/Linux/Solaris, but I'm not a Solaris expert.

Yes, it was the pass-thru. I've been using VirtualBox for several years now. I thought VirtualBox presented USB devices through an arbitration layer, but that might have been in an older version and I failed to remember the changelog.
Splitting an OVA into pieces is an option but one we are trying to avoid. Just getting a user to install VirtualBox and the extensions, then import a Solaris VM and update the extension to a new version on a training laptop sometimes requires handholding. It is not as straightforward as Windows or Linux. Re-combining a VM might be difficult, especially if we have to build and test for multiple target OSs. (Something I am sure you are very familiar with!)
Just to build a VM that could support all the require training options I had to learn bash, Windows batch, and VirtualBox CLI.
As for talking to a Solaris expert, I am trying to become one and that question of cross-filesystem access has stumped me. I have attempted multiple documented options but they all seem to fall short. I think the simplest way may be to include shared access to the local file system. Something else to discuss with the team.
I really appreciate your assistance, even if I was ultimately the cause.

spbarrett wrote:Yes, it was the pass-thru. I've been using VirtualBox for several years now. I thought VirtualBox presented USB devices through an arbitration layer, but that might have been in an older version and I failed to remember the changelog.

No, that was never the case. USB pass-through always worked this way. There is an "arbitration layer" but it works on the level of USB request blocks, below a filesystem and even below a block device.

Shared folders might be an option, of course with a different set of complications.