For the purpose of completion:
X5-2 machines support USB 2.0 compliant devices, that support a maximum power draw of 500mA.
All USB 2.0 compliant devices support this specification. Due to layout design, the front USB ports are more sensitive to this overdraw.
We may plug the HDD to the rear ports or
use a Y cable, enabling the HDD to draw power from both the USB ports.
There is a Bug 23092904 raised for this and it not being fixed, as the device is not strictly USB 2.0 compliant.