Chapter 5: Synchronization and Scheduling
Thomas Huckle, Tobias Neckel · Society for Industrial and Applied Mathematics eBooks · 2019
In order to solve specific tasks in a distributed manner, communication between and timing of jobs is necessary. In this way, time-dependent arrangements are important when connecting different computers. Otherwise, the interconnected computers cannot work together properly (similar to individual workers in a company if no meetings or consistent communication is taking place). For safety reasons, the Space Shuttle used five computers: four identical in software and hardware and one different in software. The four identical computers were running the same processes in parallel and allowed an intermediate replacement of a failing computer. The fifth computer served as the backup that had to be able to take over control in the event of a consistent failure of the other systems. The mutual connection of these different computers depended upon a very precise and timely order and coordination. Small errors might prevent this synchronization. Such a failure occurred during the first launch of the Space Shuttle in 1981.