Ianus: Guaranteeing High Performance in Solid-State Drives

Solid-state drives are becoming increasingly popular in enterprise storage systems, playing the role of large caches and permanent storage. Although SSDs provide faster random access than hard-drives, their performance under read/write workloads is highly variable to the point that it becomes worse than that of hard-drives (e.g., taking 100ms for a single read). Many systems with read/write workloads have low latency requirements, or require predictable performance and guarantees. In such cases SSD performance variability becomes a problem for both predictability and raw performance. First, we show how to provide tight throughput guarantees to multiple clients sharing the same solid-state drive storage. Second, we introduce and evaluate Ianus, a design based on redundancy, which achieves high performance, low latency and stable read throughput, as well as fault-tolerance, making it an alternative RAID-like design for solid-state drives. Finally, by combining the two solutions we provide QoS while maintaining high performance.