Optimisation des E/S disques dans les environnements multi-applicatifs distribués

National audienceScientific applications which mainly exploit non sequential accesses are more and more affected by I/O performance. In the meantime, as cluster usage grows, several applications are often executed concurrently, competing for access to storage subsystems and, thus, potentially canceling optimisations brought by Parallel I/O libraries. This article addresses the issue of disjoint accesses generated by different concurrent applications in a cluster. In such a context, good trade-off has to be assessed between performance, fairness and response time. To achieve this, an I/O scheduling algorithm together with a "requests aggregator" that considers both application access patterns and global system load, have been designed and merged into a new generic framework pluggable into any I/O file system layer