On the Trade-Offs among Performance, Energy, and Endurance in a Versatile Hybrid Drive

Abstract

There are trade-offs among performance, energy, and device endurance for storage systems. Designs optimized for one dimension or workload often suffer in another. Therefore, it is important to study the trade-offs to enable adaptation to workloads and dimensions. As Flash SSD has emerged, hybrid drives have been studied more closely. However, hybrids are mainly designed for high throughput, efficient energy consumption, or improving endurance—leaving quantitative study on the trade-offs unexplored. Past endurance studies also lack a concrete model to help study the trade-offs. Last, previous designs are often based on inflexible policies that cannot adapt easily to changing conditions. We designed and developed GreenDM , a versatile hybrid drive that combines Flash-based SSDs with traditional HDDs. The SSD can be used as cache or as primary storage for hot data. We present our endurance model together with GreenDM to study these trade-offs. GreenDM presents a block interface and requires no modifications to existing software. GreenDM offers tunable parameters to enable the system to adapt to many workloads. We have designed, developed, and carefully evaluated GreenDM with a variety of workloads using commodity SSD and HDD drives. We demonstrate the importance of versatility to enable adaptation to various workloads and dimensions.