This document proposes a technique called Dynamic Fractional Resource Scheduling (DFRS) for job scheduling on computer clusters. DFRS aims to optimize resource allocation and maximize performance using virtual machine technology. It addresses both offline and online scheduling problems. For offline problems, various bin packing heuristics are evaluated and multi-capacity bin packing performs well. For online problems, DFRS seeks to minimize maximum job stretch without relying on runtime estimates. Evaluation shows DFRS can significantly outperform traditional approaches like first-come, first-served scheduling.