The Design and Implementation of a Capacity-Variant Storage System

We present the design and implementation of a capacity-variant storage system (CVSS) for flash-based solid-state drives (SSDs). CVSS aims to maintain high performance throughout the lifetime of an SSD by allowing storage capacity to gracefully reduce over time, thus preventing fail-slow symptoms. The CVSS comprises three key components (1) CV-SSD, an SSD that minimizes write amplification and gracefully reduces its exported capacity with age; (2) CV-FS, a log-structured file system for elastic logical partition; and (3) CV-manager, a user-level program that orchestrates system components based on the state of the storage system. We demonstrate the effectiveness of CVSS with synthetic and real workloads, showing significant improvements in latency, throughput, and lifetime compared to a fixed-capacity storage system. Specifically, under real workloads, CVSS reduces the latency, improves the throughput, and extends the lifetime by 8–53%, 49–316%, and 268–327%, respectively.