Nam-Kyu Lee

High performance RAID system by using dual head disk structure

An approach for designing high performance disk array systems using a dual head disk structure is presented. In general, both I/O bandwidth and reliability can be significantly improved by using disk array systems, i.e., RAID. However, the performance of RAID systems can be significantly degraded where small read/write accesses are frequently requested. Thus, the dual head disk structure is applied to improve the performance of RAID systems. The dual head disk model can reduce not only the maximum seek time but also the average seek time by dividing the disk surface into two separated regions, one for each head. To compare the performance of the dual head RAID (DH-RAID) system with the conventional RAID systems, simulations are performed with two types of RAID configurations and several workloads. Simulation results show higher performance can be obtained by DH-RAID systems as compared with the conventional RAID systems. The DH-RAID model can provide better performance in the application environment that has a relatively high seek time ratio.

Modeling and performance analysis of dual head disk structure

A disk model with dual read/write heads is proposed to improve disk system performance. Dual head disk model can reduce the average seek distance either by selecting the closer of the two heads or by dividing the disk surface into two separated regions, one for each head. And also, because the reduced seek time can decrease any queuing delay, disk I/O response time can be reduced significantly. To compare the performance of the dual head disk model with the conventional disk model, a disk simulator in which four disk scheduling algorithms are implemented is developed. Both synthetically generated random workload and two other workloads constructed by accessing patterns traced are used for performance evaluation. Simulation results show that a higher performance by the proposed disk system as compared to the conventional disk system can be obtained under both light and heavy workloads. The dual head disk model can give better performance in the application environment that has a relatively high seek time ratio.