Real-time disk scheduling techniques for mirrored disk systems

Mirrored disk systems are currently used for enhancing reliability of disk systems as well as achieving speedup of read/write access time. These characteristics of disk mirroring can properly meet the requirements of real time applications. The paper aims to develop some techniques for management of read request queues in a mirrored disk system operating under a soft real time environment, and conduct performance comparisons between them through simulations. The simulation results show that centralized queue policies out-perform distributed queue policies, and that some improved delayed write policies can reduce the miss ratio of read requests. Finally, we suggest two improved centralized queue policies which utilize multiple delayed write queues