A low-latency storage stack for fast storage devices

Modern storage systems are facing an important challenge of making the best use of fast storage devices. Even though the underlying storage devices are being enhanced, the traditional storage stack falls short of utilizing the enhanced characteristics, as it has been optimized specifically for hard disk drives. In this article, we optimize the storage stack to maximize the benefit of low latency that fast storage devices provide. Our approach is to simplify the I/O path from application to the fast storage device by removing inefficient layers and the conventional block I/O. The proposed stack consists of three layers: an optimized device driver, a low-latency file system called L2FS, and a simplified VFS. The device driver provides a simple file I/O API to the file system instead of the existing block I/O API. L2FS, a variant of EXT4, performs low-latency I/O operations by using the file I/O API that our optimized device driver provides. We implement our storage stack on Linux 3.14.3 and evaluate it with multiple benchmarks. The results show that our system improves the throughput by up to 6.6 times and reduces the latency by an average of 54% compared to the existing storage stack on fast storage.