Originally Posted by Gripsteruser
But to give a thumbrule of Reliability - The more stuff in the system, the less reliable the system. (You're gonna be doing more maintenance to keep it running 100%.)
This is only true ceteris paribus
. In other words, the rule of thumb only applies if you are adding more stuff that has a similar failure rate to the original stuff.
Replacing a mechanical component with lots of electronic components which each have 5-9's reliability will actually increase the overall reliability of the system in most cases. Electronics have a different reliability hazard function than do mechanical components. Mechanical components tend to suffer significant infant mortality failures followed by a period of random failures, and then experience an end-of-life/wearout phase with ever increasing failure rates (mechanical wear in mechanical systems is a fact of physics). This is often called the "bathtub curve." Electronic components usually follow a decreasing failure rate curve with most failures being infant mortality failures. Wear out is by and large not an issue with electronics.
Counting the individual pixels on your display screen and transistors on your chips means there are literally millions of individual components in the device you are using to read this post. Add in all the electronic components in the internet between your device and the ADV servers and you get an inkling of just how reliable electronic components are. Electronics component reliability is orders of magnitude higher than mechanical component reliability. If it were not so, you would not be able to read this post.