I had the same problem as this and found the solution here:
Although this article is about the synthetic NIC and how to use that instead of the legacy driver it also worked for the larger drive. I created a small VHD and added it to the IDE Controller as the root partition to boot from as /dev/hda1 and then created a big VHD and added it to the SCSI Controller. When the drive was mounted it showed the full space available in fdisk.
If the hv_ modules are not loaded then I could not see the drive as a device at all.
NOTE: If you follow the above website instructions to use Synthetic NIC then you'll also need this article:
As the synthetic NIC didn't work for me until I did the above.