From what I understand, very, very large radiators every few racks. Almost as much solar panels every few racks. Radiation shielding to avoid transient errors or damage to the hardware. Then some form of propulsion for orbital corrections, I suppose. Then hauling all of this stuff to space (on a high orbit, otherwise they'd be in shade at night), where no maintenance whatsoever is possible. Then watching your hardware progressively fail and/or become obsolete every few years and having to rebuild everything from scratch again.