Error: out of disk

New install of OMV 1.0 on HP DL380 G5.
All the drive bays will be full for data drives so I am trying to boot to a
Laptop drive plugged into the internal usb port with a usb to sata adapter.
OMV installs with no errors but on reboot I get a Grub error: out of disk.

If I plug the same drive into a drive bay it boots right up.
How can I get it to boot to the drive when connected to a usb adapter.
Have tried SSD and standard laptop drive.

Thanks for the response but a google search was the first thing I tried.
Nothing I found got it working.
I was hoping someone here had ran into the same issue and fixed it.

Fixed it.
Booted to Partition Manager and resized the root partition from 78 gig to 8 gig.
It booted fine after that.