Always connect the PDU input power cords to grounded power outlets. The servers require electrical circuits to be grounded to Earth ground, and connecting the PDU power cords to grounded outlets completes the server grounding. No additional cabinet grounding is required.
Because different grounding methods vary by locality, refer to documentation such as IEC documents for the correct grounding method. Ensure that the facility administrator or qualified electrician verifies the grounding method for the building and performs the grounding work.