MixSave: Tiering-Cooperative Energy-Efficient Scheme for Hybrid Storage System

Taking advantage of green energy is becoming increasingly popular. However, when it comes to the storage I/O, where storage devices usually schedule nodes based on the intensity of the storage workload, the irregular fluctuations of green energy lead to the mismatch of peaks and valleys between green energy and storage workloads, which increases the difficulty of scheduling storage resources. To address this issue, a tiering-cooperative energy-efficient scheme for hybrid NVM-SSD storage system, called MixSave, is proposed. MixSave customizes the energy-saving strategies for each layer and tunes them cooperatively between layers, reducing overall energy usage. It efficiently tiers NVM and SSD and replicates data among them based on their performance and energy characteristics, achieving both high performance and large capacity. The workload-driven strategy is used by the NVM layer, which is used for caching, to ensure the best performance, and the number of active NVM devices depends on the storage workload. Meanwhile, the SSD layer employs a green energy-oriented strategy to conserve traditional energy, and the number of active SSD devices will be proportionally to the amount of green energy supplied. Evaluation results show that, when compared with energy-save-unaware approaches, MixSave degrades performance by less than 4% and saves traditional energy by 73% to 80% and 55% to 61% under light and heavy workloads, respectively.