Available Embedded Computer Platforms Become Reality Tutorial 1. Fault Tolerance versus High Availability Fault tolerance and high availability are not quite the same thing. Many systems today use fault-tolerant computers when the application only needs availability. Transactional reliability is needed in banking applications or in billing records for a telecommunications network.
Availability is needed in file server applications or in call-processing applications.
Traditional implementations of fault-tolerant platforms often involve proprietary hardware and software. The challenge is to provide highly available platforms without resorting to extreme or expensive measures. Availability is often expressed in percentages. A system with just 5 minutes of service outage must have 99.999 percent availability. Availability is calculated using statistical models for all the system components.