Highly Integrated Task and Resource Scheduling for Mission-Critical Systems
Horst F. Wedde, Bogdan Korel, J. Lind · 1993
We report on considerable extensions of the DRAGON SLAYER/ MELODY file system which significantly enhance Melody's missioncritical capabilities (hard real-time responsiveness, adaptability, dependability, graceful degradation, fault tolerance). Time criticality of tasks and their sensitivity with respect to latest file information are explicitly used for novel flexible task scheduling algorithms and file replication management policies, in a fully integrated model. The achieved adaptability by far outweighs the additional overhead. In order to avoid unnecessary and very costly locking of (remote) file copies, task scheduling in the MELODY model is done prior to resource/ file allocation. Although thus being based on estimates of execution times only (no guaranteed tasks), in the 2 different models of integrating task and resource scheduling developed, MELODY distinctively outperforms the classical model, most clearly in mission-critical applications.