vmdk on thumb-drive - OK on USB2 port, 'grub rescue' on USB3

[peterg4000]

I am trying to arrange a 'portable' VM - One that I can power up on 2 different hardware hosts on a regular basis. (Not at the same time)

I have created a separate VM on the 2 machines but am 'transporting' a single .vmdk on a fast USB3 thumb-drive.

I have it working fine, but for one thing:

It works without issue on a USB2 port on my laptop, but when I try a USB3 port, it goes into 'grub rescue mode' with this on the console:

error: symbol '?' not found.
Entering rescue mode...
grub rescue>

Logs attached for fresh startup through to power-down at the grub prompt above.

- Obviously the disk is readable to some extent as it managed to start grub.

I would really like to get the extra 'disk' speed of USB3.

Any ideas why it is not booting properly with vmdk on a USB3 drive?

Details:
Both hosts are Win7-64bit and have 8GB of RAM.
The guest is 32-bit Xubuntu and configured for 3024MB RAM. Guest additions are installed.
VirtualBox is updated to 4.3.15 r95713. (Latest at time of writing)
I have updated the USB3 drivers for my hardware to latest.

Thanks for any help.

[peterg4000]

I guess I just have to put up with USB2 speeds to my vmdk, huh?

No clues out there?

[loukingjr]

I guess I just have to put up with USB2 speeds to my vmdk, huh?

No clues out there?

One clue would be VirtualBox doesn't support USB3.

[socratis]

Lou, I thought about that too, but in this case VirtualBox doesn't "use" the USB3 port or device as a USB device. It simply runs from it. It shouldn't care. That's why I was puzzled by it as well, but I don't have any USB3 ports/devices to try and verify whether it works or not.

[loukingjr]

Lou, I thought about that too, but in this case VirtualBox doesn't "use" the USB3 port or device as a USB device. It simply runs from it. It shouldn't care. That's why I was puzzled by it as well, but I don't have any USB3 ports/devices to try and verify whether it works or not.

You could be right. I have lots of USB3 ports but no USB3 flash drives to test with. I was speculating since it works when plugged into a USB2 port which would "convert" a USB3 flash drive into a USB2 drive but it doesn't work when plugged into a USB3 port.

Just seemed logical.

[mpack]

The OP is using raw access? IMHO most likely the drive letter changed, invalidating the path in the VMDK descriptor.

And that's all the support I intend to provide for someone using raw access - an experts only feature.

[peterg4000]

Sorry for the delay. Had kind of given up...

@mpack - What is "raw access"? I don't think I have used that.

All I have done is put the .vmdk on an external thumb drive (FAT32 formatted, by the way), which happens to be USB3. I guess I could try it formatted as NTFS if anyone thinks it might help, but I think that creates issues if I ever want to go to a Linux host?

Like I said - It gets to the 'grub' prompt so I assume it is reading _some_ sectors off the drive.
- And I think this proves it is not "drive letter changed". I have seen that, I know what it looks like, and I am making sure it doesn't happen.

Maybe the VM behaves at 'BIOS' level when the boot sector is read, but it goes kaput when it starts to read direct... Just speculating. Don't really know how it works (Though I do believe boot sectors are read via BIOS, no?)

Anyway, I thought someone might be interested one day, as it is not far off that it could be standard practice to carry our favourite set of VMs 'on our keyring'. USB3 support (Just for the .vmdk storage) will make that snappier.

Thanks for any further thought. I will be patient.

[mpack]

Sorry, for some reason I thought you had created a raw access VMDK, but reviewing the thread now I don't remember why.

According to the log, and as has already been mentioned, your external drive is formatted using the FAT filesystem and is therefore limited to 4GB maximum size per file. Virtual disks will be corrupted if they attempt to increase beyond that size. However I don't know why that would cause problems for grub, which wouldn't be aware of the corruption. This sounds more like the typical grub errors you get after cloning a disk and hence changing the UUID.

[peterg4000]

your external drive is formatted using the FAT filesystem and is therefore limited to 4GB maximum size per file.

I am aware of that limit, but I am using the .vmdk 'split' option to get around that. I believe that functionality is long-standing and robust.
If you configure an 8Gig drive it makes 2 files that start small, and grow to a max of 4Gig.

Edit: Or maybe it's 4 files of max 2GB. Whatever - the split .vmdk feature does what it needs to do to avoid exceeding the maximum on the filesystem.

Virtual disks will be corrupted if they attempt to increase beyond that size. However I don't know why that would cause problems for grub, which wouldn't be aware of the corruption. This sounds more like the typical grub errors you get after cloning a disk and hence changing the UUID.

Well, it all works dandy if I plug the same device into a USB2 port (and it does get the same Drive letter).
I think from what you are describing, it should be equally upset on either USB port.
It's not. It's fine on a USB2 port, fails to grub on USB3.

Looks like I will have to wait until more people try to use external USB3 devices for Virtual disk storage...

[loukingjr]

As far as I know VirtualBox still does not support USB3. I could have missed a change but I don't remember seeing one. The fact that it works with USB2 but not USB3 seems to support that.

[mpack]

The USB3 part really shouldn't be relevant: VBox isn't using USB here, the host is. This isn't even a raw access drive (which might change the boot behaviour), it's just an ordinary VMDK (split2g variant).

Possibly a host or flash drive hardware or driver issue, nothing to do with VBox at all.

[loukingjr]

The USB3 part really shouldn't be relevant: VBox isn't using USB here, the host is. This isn't even a raw access drive (which might change the boot behaviour), it's just an ordinary VMDK (split2g variant).

Possibly a host or flash drive hardware or driver issue, nothing to do with VBox at all.

Not sure what I was thinking mpack . I have run guests from USB3 drives myself and I use shared folders to access USB3 drives. Chalk it up to sleep deprivation.