Flash-based solid-state drives (SSDs) have been widely adopted in various storage systems, manifesting better performance than their forerunner HDDs. However, the characteristics of flash media post some drawbacks when deploying SSD-based storage systems. First, flash media have limited program/erase cycles, making them vulnerable to media failures. Second, SSD foreground I/Os can suffer from inconsistent performance due to interference from background operations like garbage collection (GC). The major solution to the above problems is to introduce data redundancy. Redundant data can not only detect raw bit errors and recover lost data but also enable I/O scheduling to sidestep SSDs that are under performance degradation. Compared with multi-replica, data coding is a more space-efficient way to provide redundancy. However, it is more challenging to simultaneously achieve low access latency, consistent performance and fast recovery. This paper examines the design of coded storage in existing storage systems, with a focus on flash storage systems, and how they address these challenges. The coded storage techniques are categorized into in-device coding, cross-device coding, and cross-machine coding. They are designed for different scenarios and purposes, but share some design rationales in common. For each type of coded storage, we begin by presenting the theoretical bases, followed by an overview of how existing studies address the performance and endurance issues of coded storage from a systemic perspective. Finally, we review the history of coded storage, list several key insights from existing works, and speculate some promising directions for flash-oriented coded storage systems.

Zhiyue Li

Guangyan Zhang

Yang Wang

ACM Transactions on Storage

ACM TRANSACTIONS ON STORAGE (TOS) 是一本新期刊，旨在发表存储领域和密切相关学科的原始档案论文。出现在 TOS 中的文章将倾向于呈现新技术和概念，或者报告新的经验和实际系统的实验。存储是一个广泛的多学科领域，包括网络协议、资源管理、数据备份、复制、恢复、设备、安全性以及数据编码、密度和低功耗理论。这些领域之间的潜在协同作用有望开辟新的研究方向。

ACM Transactions on Storage (TOS) is an emerging academic journal dedicated to publishing original research papers in the field of storage and closely related disciplines. Articles published in TOS tend to present new technologies and concepts or report on new experiences and experimental results from practical systems. Storage is a broad multidisciplinary field that includes network protocols, resource management, data backup, replication, recovery, device security, as well as data encoding, density, and low-power theories. The potential synergies among these areas are expected to open up new research directions.

《ACM Transactions on Storage》（TOS）是一本新兴的学术期刊，专注于发表存储领域及其相关学科的原创研究论文。TOS刊登的文章通常展示新技术和概念，或报告新的经验和实际系统的实验结果。存储是一个广泛的多学科领域，涵盖网络协议、资源管理、数据备份、复制、恢复、设备安全性，以及数据编码、密度和低功耗理论等方面。这些领域之间的潜在协同作用有望开辟新的研究方向。

Category	Quartile
计算机科学	3
计算机科学, 计算机硬件	3
计算机科学, 计算机软件工程	3

Flash-oriented Coded Storage: Research Status and Future Directions

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Journal Info

Category	Quartile
COMPUTER SCIENCE, SOFTWARE ENGINEERING	2