> Even in a high availability system, hardware is a minor contributor to system outages.
[...]
> By applying the concepts of fault-tolerant hardware to software construction, software MTBF can be raised by several orders of magnitude.
[...]
> Dealing with system configuration, operations, and maintenance remains an unsolved problem.
I have no experience whatsoever with them, but I think I've seen many mentions over the years of how IBM mainframes have been designed to keep running while anything is modified or swapped out.
I also remember years ago reading about a research OS, which journaled everything such that you could supposedly pull the plug at any random moment and recover the running state with no trouble.
Link:
https://web.archive.org/web/20030430223846/http://www.eros-o...
The stability of the mainframes may be misleading, as the older isolated systems are different than the networked systems.
I would postulate that for a general purpose computer, software stability is directly proportional to connectivity.