Shushu Yi, Peking University and Zhongguancun Laboratory; Xiurui Pan, Peking University; Qiao Li, Xiamen University; Qiang Li, Alibaba; Chenxi Wang, University of Chinese Academy of Sciences; Bo Mao, Xiamen University; Myoungsoo Jung, KAIST and Panmnesia; Jie Zhang, Peking University and Zhongguancun Laboratory
All-flash array (AFA) is a popular approach to aggregate the capacity of multiple solid-state drives (SSDs) while guaranteeing fault tolerance. Unfortunately, existing AFA engines inflict substantial software overheads on the I/O path, such as the user-kernel context switches and AFA internal tasks (e.g., parity preparation), thereby failing to adopt next-generation high-performance SSDs.
Tackling this challenge, we propose ScalaAFA, a unique holistic design of AFA engine that can extend the throughput of next-generation SSD arrays in scale with low CPU costs. We incorporate ScalaAFA into user space to avoid user-kernel context switches while harnessing SSD built-in resources for handling AFA internal tasks. Specifically, in adherence to the lock-free principle of existing user-space storage framework, ScalaAFA substitutes the traditional locks with an efficient message-passing-based permission management scheme to facilitate inter-thread synchronization. Considering the CPU burden imposed by background I/O and parity computation, ScalaAFA proposes to offload these tasks to SSDs. To mitigate host-SSD communication overheads in offloading, ScalaAFA takes a novel data placement policy that enables transparent data gathering and in-situ parity computation. ScalaAFA also addresses two AFA intrinsic issues, metadata persistence and write amplification, by thoroughly exploiting SSD architectural innovations. Comprehensive evaluation results indicate that ScalaAFA can achieve 2.5× write throughput and reduce average write latency by a significant 52.7%, compared to the state-of-the-art AFA engines.
USENIX ATC '24 Open Access Sponsored by
King Abdullah University of Science and Technology (KAUST)
Open Access Media
USENIX is committed to Open Access to the research presented at our events. Papers and proceedings are freely available to everyone once the event begins. Any video, audio, and/or slides that are posted after the event are also free and open to everyone. Support USENIX and our commitment to Open Access.
![](https://www.usenix.org/sites/all/modules/usenix/usenix_files/images/usenix-locked.png)
author = {Shushu Yi and Xiurui Pan and Qiao Li and Qiang Li and Chenxi Wang and Bo Mao and Myoungsoo Jung and Jie Zhang},
title = {{ScalaAFA}: Constructing {User-Space} {All-Flash} Array Engine with Holistic Designs},
booktitle = {2024 USENIX Annual Technical Conference (USENIX ATC 24)},
year = {2024},
isbn = {978-1-939133-41-0},
address = {Santa Clara, CA},
pages = {141--156},
url = {https://www.usenix.org/conference/atc24/presentation/yi-shushu},
publisher = {USENIX Association},
month = jul
}
![](https://www.usenix.org/sites/default/files/usenix_artifact_evaluation_available_125_update.png)
![](https://www.usenix.org/sites/default/files/usenix_artifact_evaluation_functional_125.png)