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. 2020 Apr 11;20(8):2159.
doi: 10.3390/s20082159.

A Durable Hybrid RAM Disk with a Rapid Resilience for Sustainable IoT Devices

Sung Hoon Baek  1 , Ki-Woong Park  2
Affiliations

A Durable Hybrid RAM Disk with a Rapid Resilience for Sustainable IoT Devices

Sung Hoon Baek et al. Sensors (Basel). .

Abstract

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.

Keywords: IoT; direct byte read; hybrid RAM disk; operating system; secondary storage; sustainability.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Software stack for the durable hybrid RAM disk (DHRD) with direct byte read (DBR).
Figure 2
Figure 2
Software stack for the durable hybrid RAM disk (DHRD) with direct byte read(DBR).
Figure 3
Figure 3
The three primitive operations of the durable hybrid RAM disk; read, write and initialization.
Figure 4
Figure 4
Three write cases during initialization. DHRD ensures data integrity with proper policy for each case.
Figure 5
Figure 5
Software stack of DHRD for the cases of redundant memory copy and direct byte read.
Figure 6
Figure 6
The results of block-level benchmark evaluation. It plots throughputs of random read and random write workloads at block level.
Figure 7
Figure 7
SPC traces: It plots two I/O traces from online transaction processing (OLTP) applications running at two large financial institutions and three I/O traces from a popular search engine.
Figure 8
Figure 8
The results of file-level benchmark evaluation. It plots throughputs of sequential I/O, random read, random write, and mixed random read and write workloads at file level.
Figure 9
Figure 9
A benchmark using Filebench with fileserver workloads.
Figure 10
Figure 10
A generic SSHD and a DHRD-based SSHD.
Figure 11
Figure 11
The results of tiered storage in hybrid storage device. It plots I/O throughputs of tiered storage assuming that SSD, DHRD, and DBR DHRD are used as a cache tiered in a tiered storage.
Figure 12
Figure 12
A result of reading and writing for video files.
See this image and copyright information in PMC

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