X-SSD: A Storage System with Native Support for Database Logging and Replication

Transaction logging and log shipping are standard techniques to provide recoverability and high availability in data management systems. They entail an update to a local log file at every transaction and sending such an update to a remote site in a coordinated fashion. Modern databases have leveraged technologies such as Persistent Memory (PM) and RDMA-enabled networking to perform these updates as fast as possible. This mix of technologies, however, presents several drawbacks: some technologies are not portable, restricting deployments to a single class of machines; they make the data path more contrived; and they force very low-level APIs to interoperate, posing severe correctness issues. In this paper, we introduce the X-SSD, an SSD architecture that mixes NAND Flash and PM and that offers similar top performance while avoiding these issues. X-SSD devices can take transaction log writes in a fast, PM-backed data path and offer Data Propagation Services that move these writes to remote sites and eventually to NAND Flash storage. To validate this new architecture, we design and implement an actual reference X-SSD device called Villars. Our experiments show that the Villars device can manage PM and remote transfers on behalf of the database in a faster, more straightforward, and more robust way. We believe that our new architecture and reference implementation can reignite the conversation between the database and storage communities about the potential of co-designed devices.