• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.3
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• pp.107-111
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• 2023

Journaling techniques are widely used to maintain a consistent file system state in the event of a system crash. As existing journaling techniques are designed for block storage such as HDDs, they are not efficient for byte-addressable persistent memory media. This paper proposes a metadata journaling technique for in-memory file systems that has the ability of avoiding inconsistent file system states in crash situations. The proposed journaling technique reduces a large amount of writing by making use of the byte-addressable feature of memory media and bypasses heavy software I/O stack. Experimental results with the IOzone benchmark show that the proposed journaling technique improves the performance of Ext4 by 49.2% on average.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.115-117
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• 2001

대부분의 embedded system에서 hard-disk 대용으로 flash memory를 사용하고 있으며, flash device에 압축 커널이미지와 root file system image를 가지고 있다. Booting 고정 중 커널의 압축이 풀리고 메모리에 로드되어 제어를 넘겨받으면 flash memory 상에 존재하는 root file system image를 ramdisk의 image로 로드하여 시스템은 결국 ramdisk에 root file system을 가지게 된다. Ramdisk 상의 프로그램을 실행하기 위해 메모리로 실행파일 이미지를 copy하는 과정을 피하고 ramdisk 상의 이미지를 바로 프로세스의 virtual memory area에 직접 매핑 시켜 주는 XIP(eXection-In-Place)를 구현함으로써 많은 메모리 절감 효과를 얻을 수 있다. 본 연구에서는 ramdisk를 root file system으로 사용하는 embedded system에서의 XIP 구조를 설계하고 구현하였다.

• Journal of Korea Multimedia Society
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• v.11 no.3
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• pp.404-413
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• 2008

As toward a ubiquitous society, a lot of methods have been proposed to protect personal privacy. Smart Cards with CPU and Memory are widely being used to implement the methods. The use of Java Card is also gradually getting expanded into more various applications. Because there is no standards in Java Card File System, Generally, Java Card File System follows the standards of Smart Card File System. However, one of disadvantages of the Java Card File System using a standard of Smart Card File System is that inefficient memory use and increasing processing time are caused by redundancy of data and program codes. In this paper, a File Cache method and a Direct Access method are proposed to solve the problems. The proposed methods are providing efficient memory use and reduced processing time by reduce a program codes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.109-114
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• 2014

Recently the operating system share of linux on embedded system is increasing. The embedded systems on linux environment, commonly equip a file system as mini hard disk or flash memory to keep data. The types of the file system of the system are various according to it's operating system. Anyway, the more embedded system depends on the file system, the selection of the type of the file system effects more on the performance of the system. This thesis performs the performance benchmark of a FAT and Ext file systems which are most popular in embedded system. As the result, it is discussed that what file system is better at which case. These results will be a index at the selection of flash file system of the embedded systems on linux environment.

• International Journal of Contents
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• v.5 no.4
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• pp.75-80
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• 2009

Recently high-speed memory array based on RAM, which is a type of solid-state drive (SSD), has been introduced to handle the input/output (I/O) bottleneck. But there are only a few performance studies on RAM based SSD storage with regard to diverse workloads. In this paper, we focus on the file system for RAM based memory array based NGS (Next Generation Storage) system which is running on Linux operating system. Then we perform benchmark tests on practical file systems including Ext3, ReiserFS, XFS. The result shows XFS significantly outperforms other file systems in tests that represent the storage and data requests typically made by enterprise applications in many aspects. The experiment is used to design the dedicated file system for NGS system. The results presented here can help enterprises improve their performance significantly.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.4
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• pp.305-311
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• 2005

Flash memory software running on cellular phones and PDAs need to be tested extensively to cope with abrupt power and media faults. For those tests, we designed and implemented a Flash memory emulator with fault injection features. The fault injection tester has provided a helpful framework for designing fault recovery schemes and also for analyzing fault damages to the FTL (Flash Translation Layer) and file system for a Flash memory based system. In this paper, we discuss Plash memory fault types and fault injection features implemented on this Flash memory emulator. We then discuss in detail a design flaw revealed during fault injection tests. Specifically, it was revealed that a scheme that was believed to improve reliability instead, turned out to be harmful. In addition, we discuss post-fault behaviors of the FTL and the file system.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.2
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• pp.241-245
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• 2008

Non-volatile RAM (NVRAM) has both characteristics of nonvolatility and byte addressability. In order to efficiently exploit this NVRAM in the file system layer, we proposed the MiNV (Metadata in NVram) file system in our previous research. MiNV file system maintains all the metadata in NVRAM while storing file data in NAND Flash memory. In this paper, we experimentally analyze the efficiency for the execution of garbage collection in the MiNV file system. Also, we quantify the file system performance gains obtained from efficient garbage collection. Experimental results show that garbage collection on the MiNV file system executes more efficiently that on YAFFS even though these file systems adopt exactly the same garbage collection policy. Specifically, the MiNV file system invokes the aggressive garbage collection mechanism less frequently than YAFFS. Additionally, the MiNV file system postpones the first execution of the aggressive garbage collection mechanism in our experiments. From the experiments, we verify that the efficiency of garbage collection leads to performance improvements of the MiNV file system.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1705-1708
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• 2005

Recently, flash memory is becoming popular as storage system to store and retrieve multimedia files. However, there are few researches about multimedia file system for flash memory based storage devices. We have been designing and developing a novel multimedia file systems for flash memory. In this paper, we describe the semantics of real-time retrieval of multimedia data and present scheduling scheme to guarantee the real-time requirements in our multimedia file system.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.3
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• pp.171-178
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• 2015

Recently NAND flash memory has been found to be the primary cause of low performance in the smart device. NAND flash memory is different from each other the execution time of I/O operations that flash file system is required. Therefore, it is necessary to compare and analyze the flash file system I/O performance for the efficient I/O on smart device. In this paper, it was tested and analyzing the I/O performance of the YAFFS2, JFFS2, UBIFS. Experimental results most read I/O performance is good, but the writing I/O performance is not good. For UBIFS, showed a more good I/O performance compared to other flash file system.

• The Journal of the Korea Contents Association
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• v.21 no.7
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• pp.157-163
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• 2021

A single write operation in a file system can modify multiple data, but these changes in the file system are not atomically written to disk. Thus, for the consistency of the file system, conventional journaling guarantees crash consistency instead of sacrificing the system performance. It is known that using non-volatile memory as a journal space can alleviate performance degradation due to low latency and byte-level accessibility of non-volatile memory. However, none of the journaling techniques considering non-volatile memory provide scalability. In this paper, journal space on non-volatile memory is divided into multiple regions for scalable journaling, thus dispersing concentrated operations in one region. Second, the journal area-specific operator structure is used to accelerate data write operations to storage devices. We apply the proposed technique to JFS to evaluate it on multi-core servers equipped with high-performance storage devices. The evaluation results show that the proposed technique performs better than the existing technique of the NVM-based journaling file system.