Essay on Integration Engineering of Fault Tolerant Systems

What is fault tolerant system?
Systems are developed to satisfy a set of requirements that meet a need. A requirement that is important in some systems is that they be highly dependable. Fault tolerance is a means of achieving dependability. Fault tolerant system is a system which designed in such a way that it is able to operate at a reduced level rather than collapsing or becoming rudimentary completely when the some parts of that system are already malfunctioned. That is, the system as a whole is not stopped due to problems either in the hardware or the software. An example in another field is a motor vehicle designed so it will continue to be drivable if one of the tires is punctured.

Integration between hardware and software
Integration of hardware and software is very important in order to make fault tolerant system operate. There are three levels at which this can be done. In the past fault tolerance system was used only to compensate for faults in computing resources focusing only towards the hardware. By managing extra hardware resources, the computer subsystem increases its ability to continue operation. Hardware fault tolerancemeasures include redundant communications, replicated processors, additional memory, and redundant power/energy supplies. (Siewiorek, 1995)

At times it is also possible that the fault is not from the end of the hardware but from the software side so it is equally important that along with the hardware the software must be equally compatible such as for changes in program or data structures due to transients or design errors. This is software fault tolerance. Mechanisms such as checkpoint/restart, recovery blocks and multiple-version programs are often used at this level. (Spainhower, 1998)

The computer subsystem at times may also provide functions that compensate for failures.................

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