SIRF-1: Enhancing Reliability of Single Flash SSD through Internal Mirroring for Mission-Critical Mobile Applications

Flash memory based solid state drives (SSD) are increasingly common in portable and mobile computing devices such as laptops, mobile phones, and tablets. Due to space, weight, and power constraints, portable devices are often restricted to a single storage device, which makes them susceptible to data loss from internal errors. On the other hand, mission-critical mobile applications like wireless healthcare always demand a high level of data reliability. This is mainly because data sampled from mobile and dynamic environments are most likely irreproducible. An effective approach to improving storage and data reliability is the RAID (redundant arrays of inexpensive disks) organization. However, the multiple disks required to implement RAID make it incompatible with the aforementioned restrictions of many portable devices. In this paper, we propose a SIRF (single internally redundant flash) architecture that leverages the internal hierarchical structure and parallelism of SSDs to provide redundancy similar to RAID in a single drive configuration. The initial effort focuses on implementing SIRF-1 (mirroring), which is the corollary to its RAID-1 counterpart. In SIRF-1, data is mirrored across SSD channels to optimally exploit parallelism for both read and write operations. Simulation results show that for read-dominant workloads SIRF-1 significantly outperforms a non-mirrored SSD by up to 39.5% in terms of mean response time. For write-intensive workloads, SIRF-1 pays a performance penalty no more than 5.5%.