I have put the debian system downloaded from here onto a SD card.
Then used the 'VBoxManage internalcommands createrawvmdk -filename path\to\usb.vmdk -rawdisk \\.\PhysicalDrive1' command to create a vndk file pointing to the SD card.
When I try to use this in VirtualBox at the add hard disk option under IDE controller in storage settings I get this error
Failed to open the hard disk F:\Rasp Pi\VirtualBox\mystuff\usb.vmdk
The medium 'F:\Rasp Pi\VirtualBox\mystuff\usb.vmdk' can't be used as the requested device type.
Am I doing something wrong or is it not possible to use the SD card in this way?