Horst F. Wedde, Alijani G. S., W. G. Brown, S. Chen und B. K. Kim
Operating System Support for Adaptive Real-Time Systems
ACM Operating System Reviews, Nr. 23 (3), 1989
We analyze current and future needs in building adaptive real-time systems, and then formulate a series of design requirements for their hardware/interconnection, operating system, and application levels from which we derive a plea for a layered and integrated system design. We report on the novel distributed operating system DRAGON SLAYER which provides highly reliable and adaptive kernel services for real-time applications. It supports the novel file system MELODY which, in order to both meet real-time constraints and provide for high availability in a hazardous environment, allows for replicati~g, relocating, or deleting of file copies. Such copies may also assume a different status regarding the recency, reliability, and consistency of their information: They may be public or private. Status changes as well as file replication, deletion, or relocation are analyzed and manal,~ed by local file assigners, based on cost and time delay criteria and - for public copies - on cooperation with all file assigners responsible for the other public copies of a given file. A distributed implementation of our integrated system design model is currently being completed itt our labs in order to serve as a distributed real-time testbed. For systems modeled according to our design requirements all relevant parameters could be checked and fine-tuned according to the environmental situation for the tested system.- We also report on a sensitivity study that shows how promptly the MELODY file system reacts to changing environmental situations (changing request patterns). Our findings are discussed, future work is outlined.