I was on the Triumph sometime ago. It is a total electric drive ship. There six 10 MW generators for propulsion and auxiliaries. The toilets flush by vacuum and use very little water. The flush stuff is all handled by vacuum because there is not enough fall to slope the pipes.
Fresh water is produced by either vacuum distillation or reverse osmosis. Large amounts of power are required for meal preparation, refrigeration, and lighting. Emergency generators are located very high on the vessel, but because they are above the center of buoyancy introduce a large rolling moment.
It would certainly make sense to completely isolate and compartmentalize the propulsion generators, switch gear, support services etc to provide complete redundancy. I have to believe that is done to some extent. Very large container ships and crude oil carries have only 1 direct drive diesel. When it goes down it is tow time.