Engine failure - VPLEX Local

I have a customer concerned about whether or not a VPLEX engine is a single point of failure.   I do understand that multiple engines can be clustered together, but was curious if anyone has thoughts on just what could cause a single engine/chassis failure?   I'm not coming up with much other than some catastrophic power surge that smokes the unit (which would probably smoke everything else in the data center cage for that matter), sprinkler head goes off above the unit, etc.   To my knowledge, the engine chassis doesn't really have any moving parts.   Does it even have a CMI bus going over a backplane?  I don't see a CMI bus shown on architecture diagrams.  I have experienced a bad backplane before in my lifetime on an older Celerra NS500 device.

Thanks!