Exploring Storage Class Memory with Key Value Stores

In the near future, new storage-class memory (SCM) tech-nologies – such as phase-change memory and memristors – will radically change the nature of long-term storage. These devices will be cheap, non-volatile, byte addressable, and near DRAM density and speed. While SCM offers enormous oppor-tunities, profiting from them will require new storage systems specifically designed for SCM’s properties. This paper presents Echo, a persistent key-value storage sys-tem designed to leverage the advantages and address the chal-lenges of SCM. The goals of Echo include high performance for both small and large data objects, recoverability after fail-ure, and scalability on multicore systems. Echo achieves its goals through the use of a two-level memory design targeted for memory systems containing both DRAM and SCM, ex-ploitation of SCM’s byte addressability for fine-grained trans-actions in non-volatile memory, and the use of snapshot isola-tion for concurrency, consistency, and versioning. Our evalua-tion demonstrates that Echo’s SCM-centric design achieves the durability guarantees of the best disk-based stores with the per-formance characteristics approaching the best in-memory key-value stores