[CentOS] CentOS 7 not installable using KVM-over-IP System

Hi,
I just tried to install CentOS 7 using a Lantronix Spider KVM-over-IP
System and its virtual media feature and to my surprise this did not work.
The installation using the netinstall iso seems to work for a while (I
see some dracut boot messages) but when the first stage of the boot is
finished I get dropped into an emergency shell with the error message
that "/dev/root does not exist".

I tried this on a Supermicro system and a gen-8 HP ProLiant Server both
with the same result.

Using CentOS 6 instead worked fine and I could install the Systems
without issues.

Any idea what the problem could be? Given that the iso is passed through
as a USB storage device I'm not sure what the problem could be.

Regards,
   Dennis