Erlang was reported to have been used in production systems for over 20 years with an uptime percentage of 99.9999999%. I did the math as the following: 20*365.25*24*60*60*(1 - 0.999999999) == 0.631 s That means the system only has less than one second of downtime during the period of 20 years. I am not trying to challenge the validity of this, I am just curious about how we can shut down a system
![Erlang's 99.9999999% (nine nines) reliability](https://cdn-ak-scissors.b.st-hatena.com/image/square/98d6f053a97a87156775f60757c60865d0f2c47d/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fstackoverflow%2FImg%2Fapple-touch-icon%402.png%3Fv%3D73d79a89bded)