"A critical model of the engineering profession is that of backup systems. A good engineer never assumes the perfect reliability of the components of the system. He or she builds in redundancy to protect the integrity of the total system. Without the application of this robustness principle, tangible and intangible systems tend to fail over time." - Shane Parrish "In reliability engineering, redundancy is defined as the existence of more than one means for accomplishing a given task. Thus all of these means must fail before there is a system failure. A Backup System is turning a Multiplicative System with a single break point into an additive system with two or more break points. How to use this mental model: Analyze the primary system - Is the primary system a multiplicative one or additive one ? If the system if additive, by definition it doesn't need a backup system. if the primary system is a simple or complex one ? If the system is a simple one, other means of increasing reliability could be more effective( margin of safety ) - Designing Backup System. if the primary system is a complex and multiplicative one, adding backup system could greatly improve reliability." - James Clear
Shane Parrish's Farnam Street Mental Model Guide https://www.farnamstreetblog.com/mental-models/ --- James Clear Mental Models Overview https://jamesclear.com/mental-models https://rationalpov.gitbooks.io/mental-model/content/discipline_engineering,backup_systemredundancy.html