OS support for fault tolerance

[perryh at pluto.rain.com]

"Dieter BSD" <dieterbsd at engineer.com> wrote:

> The problem then is how to feed both machines the same inputs, and
> compare the outputs. ??Do we need a third machine to supervise?
> Can we have each machine keep an eye on the other, avoiding the
> need for a third machine?

A pair would work as long as the only failures are "obvious" (e.g.
crashes).  If they simply disagree as to the result, how would we
determine which one was right?

> Which then leads to the issue of how to avoid problems when *it*
> breaks.

For some reason, this reminds me of a Dr. Seuss story:
http://www.goodreads.com/review/show/49519038