SOYA: SSD-based RAID systems reliability simulator

Abstract

The use of Solid State Drives (SSDs) has been increased in storage systems due to high performance and low power consumption. However, some inherent properties of SSDs result in different behavior for SSDs in comparison with Hard Disk Drives (HDDs). As an inherent property, the Bit Error Rate (BER) of SSDs increases, when the number of Program/Erase (P/E) cycles arises. This increment leads to two effects in an array of SSDs during its operation: (1) different BER on different SSDs of the system (SSD-variant BER), and (2) different BER in different time moments (time-variant BER). With respect to these two effects, the reliability evaluation of SSD-based RAIDs would be different from HDD-based RAlDs. This paper introduces a simulator called SOYA for evaluating the reliability of RAH) systems regarding different BER of SSDs. Both time-variant BER and SSD-variant BER have been considered in the evaluation process of this simulator. This simulator provides the ability to compare the reliability of SSD-based RAID systems considering arbitrary parameters in the evaluation such as disk failure rate, disk repair time, RAID-controller failure rate, RAID-controller repair time, and different levels of reliability. SOYA is the first SSD-based reliability simulator for SSD-bases RAID systems which can consider all the above-mentioned parameters together in its reliability evaluation.