I/O Interface Independence with xNVMe

The tight coupling of data-intensive systems and I/O interface has been a problem for years. A database system, relying on an specific I/O backend for direct asynchronous I/Os such as libaio, inherits its limitations in terms of portability, expressiveness and performance. The emergence of high-performance NVMe Solid-State Drives (SSDs), enabling new command sets, compounds this problem. Indeed, efforts to streamline the I/O stack have led to the introduction of new, complex and idiosyncratic I/O interfaces such as SPDK, io_uring or asynchronous ioctls. What is the appropriate I/O interface for a given system? How can applications effectively leverage SSD and end-to-end I/O interface innovations? Is I/O interface lock-in a necessary evil for data-intensive systems and storage services? Our answer to the latter question is no. Our answer to the former questions is xNVMe, a cross-platform user-space library that provides I/O-interface independence to user-space software. In this paper, we present the xNVMe API, we detail its design and we show that xNVMe has a negligible cost atop the most efficient I/O interfaces on Linux, FreeBSD and Windows.