SafeStore: A Durable and Practical Storage System

This paper presents SafeStore, a distributed storage system designed to maintain long-term data durability despite conventional hardware and software faults, environmental disruptions, and administrative failures caused by human error or malice. The architecture of SafeStore is based on fault isolation, which SafeStore applies aggressively along administrative, physical, and temporal dimensions by spreading data across autonomous storage service providers (SSPs). However, current storage interfaces provided by SSPs are not designed for high end-to-end durability. In this paper, we propose a new storage system architecture that (1) spreads data efficiently across autonomous SSPs using informed hierarchical erasure coding that, for a given replication cost, provides several additional 9's of durability over what can be achieved with existing black-box SSP interfaces, (2) performs an efficient end-to-end audit of SSPs to detect data loss that, for a 20% cost increase, improves data durability by two 9's by reducing MTTR, and (3) offers durable storage with cost, performance, and availability competitive with traditional storage systems. We instantiate and evaluate these ideas by building a SafeStore-based file system with an NFS-like interface.