Baek Sung Hoon, Park Ki-Woong
Department of Computer System Engineering, Jungwon University, Chungcheongbuk-do 28024, Korea.
Department of Computer and Information Security, Sejong University, Seoul 05006, Korea.
Sensors (Basel). 2020 Apr 11;20(8):2159. doi: 10.3390/s20082159.
Flash-based storage is considered to be a de facto storage module for sustainable Internet of things (IoT) platforms under a harsh environment due to its relatively fast speed and operational stability compared to disk storage. Although their performance is considerably faster than disk-based mechanical storage devices, the read and write latency still could not catch up with that of Random-access memory (RAM). Therefore, RAM could be used as storage devices or systems for time-critical IoT applications. Despite such advantages of RAM, a RAM-based storage system has limitations in its use for sustainable IoT devices due to its nature of volatile storage. As a remedy to this problem, this paper presents a durable hybrid RAM disk enhanced with a new read interface. The proposed durable hybrid RAM disk is designed for sustainable IoT devices that require not only high read/write performance but also data durability. It includes two performance improvement schemes: rapid resilience with a fast initialization and direct byte read (DBR). The rapid resilience with a fast initialization shortens the long booting time required to initialize the durable hybrid RAM disk. The new read interface, DBR, enables the durable hybrid RAM disk to bypass the disk cache, which is an overhead in RAM-based storages. DBR performs byte-range I/O, whereas direct I/O requires block-range I/O; therefore, it provides a more efficient interface than direct I/O. The presented schemes and device were implemented in the Linux kernel. Experimental evaluations were performed using various benchmarks at the block level till the file level. In workloads where reads and writes were mixed, the durable hybrid RAM disk showed 15 times better performance than that of Solid-state drive (SSD) itself.
基于闪存的存储由于其速度相对较快且与磁盘存储相比具有操作稳定性，被认为是恶劣环境下可持续物联网（IoT）平台的实际存储模块。尽管它们的性能比基于磁盘的机械存储设备快得多，但读写延迟仍无法赶上随机存取存储器（RAM）。因此，RAM可作为对时间要求苛刻的物联网应用的存储设备或系统。尽管RAM有这些优点，但基于RAM的存储系统由于其易失性存储的性质，在可持续物联网设备中的使用存在局限性。作为解决此问题的一种方法，本文提出了一种通过新的读取接口增强的耐用混合RAM磁盘。所提出的耐用混合RAM磁盘专为不仅需要高读写性能而且需要数据耐久性的可持续物联网设备而设计。它包括两种性能改进方案：快速初始化的快速恢复能力和直接字节读取（DBR）。快速初始化的快速恢复能力缩短了初始化耐用混合RAM磁盘所需的长时间启动时间。新的读取接口DBR使耐用混合RAM磁盘能够绕过磁盘缓存，磁盘缓存是基于RAM的存储中的一项开销。DBR执行字节范围的I/O，而直接I/O需要块范围的I/O；因此，它提供了比直接I/O更高效的接口。所提出的方案和设备在Linux内核中实现。使用从块级别到文件级别的各种基准进行了实验评估。在读写混合的工作负载中，耐用混合RAM磁盘的性能比固态硬盘（SSD）本身高出15倍。
