Is there any motivation to achieve SixSigma or similar in DevOps?
This may sound mean but 6 Sigma does not translate that well to computer systems. The general ideas are valid but the numbers are not. It is intended for the meat world, not a place were we routinely do calculations on gigs or tb's of data a day. Assume you run 1 trillion operations (not much when a regular desktop computer can do ~12 billion a second) at 99.99966% success you are still failing 350k times! 


Yes, most of the operations on the code side will actually be made up of multiple CPU operations
Yes, some of this is caught by hardware via ECC etc


What would stand up would be trying to use S6 against the changes you make to a computer system (code pushes or otherwise). Not the operation of existing code (which needs a much higher level of reliability than what you'd use to evaluate PPM on a shop floor for physically created stuff).