An Embedded FTL for SSD RAID

Solid State Disk (SSD) storage systems are the storage medium of choice in modern embedded devices, and so the performance, lifespan, and reliability of these devices is an increasing issue in many application domains. Previous work has proposed adaptations to RAID architectures to render them suitable for SSD systems. However these solutions open a number of challenges such as wear-levelling across the array, efficient address translation and fast access times. In this paper we present an adaptation to the Flash Translation Layer of an SSD controller that offers firstly reliability enhancement under both sequential and random write patterns, secondly a forced random write technique that permits novel wear-levelling algorithms, thirdly a dynamic data allocation policy at page level, and fourthly the meta data storage mechanism by introducing non-volatile SRAM (nvSRAM) for mapping and caching data. Our experimental results show that this FTL design makes RAIDbased SDD storage systems more reliable regardless of workload characteristics. Our implementation in synthesizable Verilog is shown to be amenable to further investigations and experiments.