Fault-tolerant architecture allows a system to continue working even when part of the system fails. Fault-tolerant servers provide continuous availability through hardware failures by utilizing and operating redundant components. Mark McCarthy posted this definition on Tech Target, which we feel is a great simplified definition. He states:

“Fault-tolerant describes a computer system or component designed so that, in the event that a component fails, a backup component or procedure can immediately take its place with no loss of service.”