Department of Computer Engineering,Sharif University of Technology, Tehran, Iran
Over the past decades, Redundant Array of independent Disks (RAIDs) have been configured based on mechanical characteristics of Hard Disk Drives (HDDs). With the advent of Solid-State Drives (SSDs), such configurations such as stripe unit size can be far from the characteristics of SSDs. In this paper, we investigate the effect of stripe unit size on the endurance and the overall I/O performance of an SSD-based RAID array and compare the optimal stripe unit size with the suggested stripe unit sizes for HDD-based RAID. To this end, we first examine the number of extra page reads and writes imposed by write requests and then observe the corresponding impact on the overall throughput and the average response time of SSD-based RAID arrays. The effect of extra page writes for different stripe unit sizes and their impact on endurance has been also examined. To validate the analytical study, we have used I/O intensive traces and simulated an SSD-based RAID array using DiskSim simulator with different stripe unit sizes. The experimental results reveal that unlike HDD-based RAID arrays, a 4KB stripe unit size can significantly improve the throughput, response time, and endurance of an SSD-based RAID4 array (up to 67.6%, 52.2%, and 48.6%, respectively) as compared to 128KB stripe unit size.