HIOPS-KV: Exploiting multiple flash solid-state drives for key value stores

Current key value stores rely on DRAM based inmemory architectures where scalability is limited by high power and low density of DRAM. As an alternative, flash SSDs has been explored because of the merits of low power, high density and high internal parallelism. However, the unpredictable latency caused by SSD internal resource conflicts challenges the use of flash SSDs. To address this issue, we present HIOPS-KV a storage I/O software stack for key value stores. HIOPS-KV exploits multiple solid-state drives (SSDs) to control the latencies. With replicas, HIOPS-KV avoids structural collisions which cause long latency operations by spreading colliding operations to distinct devices. For evaluation, we integrated HIOPS-KV into memcached on a low cost high IOPS SSD system built with PC components. At 32 YCSB clients, our system was capable of 117k ops/sec with 263 us average latency showing approximately 4ms at the 99th percentile latency.