• Title/Summary/Keyword: In-memory file system

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Temporary Metadata Journaling Scheme to Improve Performance and Stability of a FAT Compatible File System (FAT 파일 시스템의 호환성을 유지하며 성능과 안정성을 향상시키는 메타데이터 저널링 기법의 설계)

  • Hyun, Choul-Seung;Choi, Jong-Moo;Lee, Dong-Hee;Noh, Sam-H.
    • Journal of KIISE:Computer Systems and Theory
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    • v.36 no.3
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    • pp.191-198
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    • 2009
  • The FAT (File Allocation Table) compatible file system has been widely used in mobile devices and memory cards because of its data exchangeability among numerous platforms recognizing the FAT file system. By the way. modern embedded systems have tough demands for instant power failure recovery and superior performance for multimedia applications. The key issue is how to achieve the goals of superior write performance and instant booting capability while controlling compatibility issues. To achieve the goals while controlling compatibility issues. we devised a temporary meta-data journaling scheme for a FAT compatible file system. Benchmark results of the scheme implemented in a FAT compatible file system shows that it really improves write performance of the FAT file system by converting small random write for meta-data update to a large sequential write in journaling area. Also, it provides natural way to implement the instant booting capability. Nevertheless, the file system compatibility is temporarily compromised by the scheme because it stores updated meta-data in the temporary journaling area rather than to their original locations. However, the compatibility can be fully recovered at any time by journal-flushing that copies meta-data in journaling area to their original locations. Generally, the journal-flushing is done before un-mounting a memory card so that it can be used in other mobile devices which recognized FAT file system but not the temporary meta-data journaling scheme.

Lightweight Capability-Based Access Control System on File Descriptor via ARM PA (ARM PA를 통한 경량화된 파일 디스크립터 권한 관리 시스템)

  • Kyuwon Cho;Hojoon Lee
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.33 no.2
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    • pp.319-323
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    • 2023
  • In intra-process isolation, file descriptors work as another attack vector from the memory corruption attacks. The attacker can read or write by corrupting file descriptors so they can escape the isolation. In this paper, we propose new lightweight capability-based access control system on file descriptor using ARM's hardware extension, PA(Pointer Authentication). Our system was implemented on Linux kernel module, only shows 5% overhead to control the access on the file descriptor.

Development of the Integrated Loader/Linker System for the Java Class File and .NET PE File. (자바 클래스 파일과 .NET PE 파일을 위한 통합 로더/링커 시스템의 개발)

  • Ko, Kwang-Man
    • Journal of Korea Multimedia Society
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    • v.10 no.11
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    • pp.1472-1482
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    • 2007
  • The integrated loader/linker plays a very important role in creating all types of information and ensuring information integrity needed for substantial executions by receiving a PE input file, an intermediate representation of a java class file or a .NET environment, thereby allowing for saving information optimized for verification, resolution, initialization, and execution. This paper proposes a loader/linker system for integrating a java class file and .NET-based PE file. As a means of implementing the loader/linker system, a new execution file format(*.evm) and a memory format were designed to save all information of Java class files and .NET-based PE files, and enable the information in those files to be executed in a JVM or .NET environment through the use of saved execution information.

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Design and Implementation of an In-Memory File System Cache with Selective Compression (대용량 파일시스템을 위한 선택적 압축을 지원하는 인-메모리 캐시의 설계와 구현)

  • Choe, Hyeongwon;Seo, Euiseong
    • Journal of KIISE
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    • v.44 no.7
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    • pp.658-667
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    • 2017
  • The demand for large-scale storage systems has continued to grow due to the emergence of multimedia, social-network, and big-data services. In order to improve the response time and reduce the load of such large-scale storage systems, DRAM-based in-memory cache systems are becoming popular. However, the high cost of DRAM severely restricts their capacity. While the method of compressing cache entries has been proposed to deal with the capacity limitation issue, compression and decompression, which are technically difficult to parallelize, induce significant processing overhead and in turn retard the response time. A selective compression scheme is proposed in this paper for in-memory file system caches that rapidly estimates the compression ratio of incoming cache entries with their Shannon entropies and compresses cache entries with low compression ratio. In addition, a description is provided of the design and implementation of an in-kernel in-memory file system cache with the proposed selective compression scheme. The evaluation showed that the proposed scheme reduced the execution time of benchmarks by approximately 18% in comparison to the conventional non-compressing in-memory cache scheme. It also provided a cache hit ratio similar to the all-compressing counterpart and reduced 7.5% of the execution time by reducing the compression overhead. In addition, it was shown that the selective compression scheme can reduce the CPU time used for compression by 28% compared to the case of the all-compressing scheme.

Design and Implementation of the Flash File System that Maintains Metadata in Non-Volatile RAM (메타데이타를 비휘발성 램에 유지하는 플래시 파일시스템의 설계 및 구현)

  • Doh, In-Hwan;Choi, Jong-Moo;Lee, Dong-Hee;Noh, Sam-H.
    • Journal of KIISE:Computer Systems and Theory
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    • v.35 no.2
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    • pp.94-101
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    • 2008
  • Non-volatile RAM (NVRAM) is a form of next-generation memory that has both characteristics of nonvolatility and byte addressability each of which can be found in nonvolatile storage and RAM, respectively. The advent of NVRAM may possibly bring about drastic changes to the system software landscape. When NVRAM is efficiently exploited in the system software layer, we expect that the system performance can be significantly improved. In this regards, we attempt to develop a new Flash file system, named MiNVFS (Metadata in NVram File System). MiNVFS maintains all the metadata in NVRAM, while storing all file data in Flash memory. In this paper, we present quantitative experimental results that show how much performance gains can be possible by exploiting NVRAM. Compared to YAFFS, a typical Flash file system, we show that MiNVFS requires only minimal time for mounting. MiNVFS outperforms YAFFS by an average of around 400% in terms of the total execution time for the realistic workloads that we considered.

Boosting up the Mount Latency of NAND Flash File System using Byte-addressable NVRAM (바이트 접근성을 가지는 비휘발성 메모리 소자를 이용한 낸드 플래시 파일 시스템의 부팅시간 개선 기법)

  • Jeon, Byeong-Gil;Kim, Eun-Ki;Shin, Hyung-Jong;Han, Seok-Hee;Won, Yoo-Jip
    • Journal of KIISE:Computing Practices and Letters
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    • v.14 no.3
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    • pp.256-260
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    • 2008
  • This paper describes an improvement of mount-time delay in NAND Flash file systems. To improve file system mount performance, this work configures a hierarchical storage system with byte-addressable NVRAM and NAND Flash memory, and let the meta data of a file system allocated in the NVRAM. Since the meta data are stored in NVRAM supporting data integrity some of the items, which are stored in Spare area and Object Header area of NAND Flash memory to control meta data of NAND Flash file system, could be eliminated. And also, this work eliminates the scanning operation of the Object Header area of previous work FRASH1.0. The scanning operation is definitely required to find out the empty Object Header address for storing the Object Header data and provokes a certain amount of performance loss in file generation and deletion. In this work, an implemented file system, so-called FRASH1.5, is demonstrated, featuring new data structures and new algorithms. The mount time of FRASH1.5 becomes twice as fast as that of the FRASH1.0. The performance in file generation gets improved by about $3{\sim}8%$. In particular, for most large-size files, the FRASH1.5 has 8 times faster mount time than YAFFS, without any performance loss as seen in the file generation.

New Flash Memory Management Method for Reliable Flash Storage Systems (신뢰성 있는 플래시메모리 저장시스템 구축을 위한 플래시메모리 저장 공간 관리 방법)

  • Kim, Han-Joon;Lee, Sang-Goo
    • Journal of KIISE:Computer Systems and Theory
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    • v.27 no.6
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    • pp.567-582
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    • 2000
  • We propose a new way of managing flash memory space for flash memory-specific file system based on log-structured file system. Flash memory has attractive features such as non-volatility, and fast I/O speed, but it also suffers from inability to update in place and limited usage cycles. These drawbacks require many changes to conventional storage (file) management techniques. Our focus is on lowering cleaning cost and evenly utilizing flash memory cells while maintaining a balance between the two often-conflicting goals. The proposed cleaning method performs well especially when storage utilization and the degree of locality are high. The cleaning efficiency is enhanced by dynamically separating cold data and non-cold data. The second goal, cycle-leveling is achieved to the degree where the maximum difference between erase cycles is below the error range of the hardware. Simulation results show that the proposed method has significant benefit over naxve methods: maximum of 35% reduction in cleaning cost with even spreading writes across segments.

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Design and Implementation of Flash Cryptographic File System Based on YAFFS (YAFFS 기반의 암호화 플래시 파일 시스템의 설계 및 구현)

  • Kim, Seok-Hyun;Cho, Yoo-Kun
    • Convergence Security Journal
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    • v.7 no.4
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    • pp.15-21
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    • 2007
  • As the amount of flash memory being used in embedded device is increased and embedded devices become more important in many computing environments, embedded file system security becomes more important issue. Moreover embedded devices can be easily stolen or lost because of it's high portability. If the lost embedded device has very important information, there's no means to protect it except data encryption. For improving embedded devices' security this paper propose design and implementation of flash cryptographic file system. For this purpose YAFFS is used. By the modified YAFFS cryptographic file system, the security of embedded devices can be improved.

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Design and Implementation of Kernel-Level Split and Merge Operations for Efficient File Transfer in Cyber-Physical System (사이버 물리 시스템에서 효율적인 파일 전송을 위한 커널 레벨 분할 및 결합 연산의 설계와 구현)

  • Park, Hyunchan;Jang, Jun-Hee;Lee, Junseok
    • IEMEK Journal of Embedded Systems and Applications
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    • v.14 no.5
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    • pp.249-258
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    • 2019
  • In the cyber-physical system, big data collected from numerous sensors and IoT devices is transferred to the Cloud for processing and analysis. When transferring data to the Cloud, merging data into one single file is more efficient than using the data in the form of split files. However, current merging and splitting operations are performed at the user-level and require many I / O requests to memory and storage devices, which is very inefficient and time-consuming. To solve this problem, this paper proposes kernel-level partitioning and combining operations. At the kernel level, splitting and merging files can be done with very little overhead by modifying the file system metadata. We have designed the proposed algorithm in detail and implemented it in the Linux Ext4 file system. In our experiments with the real Cloud storage system, our technique has achieved a transfer time of up to only 17% compared to the case of transferring split files. It also confirmed that the time required can be reduced by up to 0.5% compared to the existing user-level method.

Performance Enhancement and Evaluation of Distributed File System for Cloud (클라우드 분산 파일 시스템 성능 개선 및 평가)

  • Lee, Jong Hyuk
    • KIPS Transactions on Computer and Communication Systems
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    • v.7 no.11
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    • pp.275-280
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    • 2018
  • The choice of a suitable distributed file system is required for loading large data and high-speed processing through subsequent applications in a cloud environment. In this paper, we propose a write performance improvement method based on GlusterFS and evaluate the performance of MapRFS, CephFS and GlusterFS among existing distributed file systems in cloud environment. The write performance improvement method proposed in this paper enhances the response time by changing the synchronization level used by the synchronous replication method from disk to memory. Experimental results show that the distributed file system to which the proposed method is applied is superior to other distributed file systems in the case of sequential write, random write and random read.