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  • Tomonori Fujita, Masanori Ogawara
    Information and Media Technologies
    2006年 1 巻 1 号 626-638
    発行日: 2006年
    公開日: 2006/06/15
    ジャーナル フリー
    Arbre is a file system that guarantees the integrity of the entire file system on an untrusted remote block-level storage system with a small amount of trusted storage. Arbre does not require changes to the remote block-level storage systems commercially available today. Even if an unauthorized person manages to get complete access to the storage system, they cannot modify or replay any data without being detected. This is achieved by organizing all file system blocks as a single tree and storing their hashes as a part of metadata to later verify the correctness of their contents.
  • Tomonori Fujita, Masanori Ogawara
    IPSJ Digital Courier
    2005年 1 巻 381-393
    発行日: 2005年
    公開日: 2005/09/14
    ジャーナル フリー
    Arbre is a file system that guarantees the integrity of the entire file system on an untrusted remote block-level storage system with a small amount of trusted storage. Arbre does not require changes to the remote block-level storage systems commercially available today. Even if an unauthorized person manages to get complete access to the storage system, they cannot modify or replay any data without being detected. This is achieved by organizing all file system blocks as a single tree and storing their hashes as a part of metadata to later verify the correctness of their contents.
  • Seung-Wan JUNG, Young Jin NAM, Dae-Wha SEO
    IEICE Transactions on Information and Systems
    2011年 E94.D 巻 11 号 2259-2270
    発行日: 2011/11/01
    公開日: 2011/11/01
    ジャーナル フリー
    Recently, the need for multimedia devices, such as mobile phones, digital TV, PMP, digital camcorders, digital cameras has increased. These devices provide various services for multimedia file manipulation, allowing multimedia contents playback, multimedia file editing, etc. Additionally, digital TV provides a recorded multimedia file copy to a portable USB disk. However, Linux Ext3 file system, as employed by these devices, has a lot of drawbacks, as it required a considerable amount of time and disk I/Os to store large-size edited multimedia files, and it is hard to access for typical PC users. Therefore, in this paper a design and implementation of an amortized Ext3 with FWAE (Fast Writing-After-Editing) for WinXP-based multimedia applications is described. The FWAE is a fast and efficient multimedia file editing/storing technique for the Ext3 that exploits inode block pointer re-setting and shared data blocks by simply modifying metadata information. Individual experiments in this research show that the amortized Ext3 with FWAE for WinXP not only dramatically improves written performance of the Ext3 by 16 times on average with various types of edited multimedia files but also notably reduces the amount of consumed disk space through data block sharing. Also, it provides ease and comfort to use for typical PC users unfamiliar with Linux OS.
  • Seung-Ho Lim
    IEICE Electronics Express
    2011年 8 巻 6 号 372-377
    発行日: 2011年
    公開日: 2011/03/25
    ジャーナル フリー
    Flash file systems are used for flash memory-based storage devices for more efficient use of flash memory. In the file system, metadata, especially directory management, is one of the crucial management points to enhance storage system performance. In this paper, we present an efficient directory management scheme of flash memory based file system for giga scale flash memory. Specifically, we design the hash-based directory architecture for directory management and indexing structure for file index management. The hash-based directory management can reduce redundant write operations of flash memory. It can also reduce the file system mount time and memory usage during runtime.
  • Naohiro AOTA, Kenji KONO
    IEICE Transactions on Information and Systems
    2019年 E102.D 巻 2 号 269-279
    発行日: 2019/02/01
    公開日: 2019/02/01
    ジャーナル フリー

    Modern file systems, such as ext4, btrfs, and XFS, are evolving and enable the introduction of new features to meet ever-changing demands and improve reliability. File system developers are struggling to eliminate all software bugs, but the operating system community points out that file systems are a hotbed of critical software bugs. This paper analyzes the code coverage of xfstests, a widely used suite of file system tests, on three major file systems (ext4, btrfs, and XFS). The coverage is 72.34%, and the uncovered code runs into 23,232 lines of code. To understand why the code coverage is low, the uncovered code is manually examined line by line. We identified three major causes, peculiar to file systems, that hinder higher coverage. First, covering all the features is difficult because each file system provides a wide variety of file-system specific features, and some features can be tested only on special storage devices. Second, covering all the execution paths is difficult because they depend on file system configurations and internal on-disk states. Finally, the code for maintaining backward-compatibility is executed only when a file system encounters old formats. Our findings will help file system developers improve the coverage of test suites and provide insights into fostering the development of new methodologies for testing file systems.

  • TOMOAKI TOGASHI, TAKAOMI MURAKAMI, KIYOSHI KATO
    素粒子論研究
    2007年 115 巻 3 号 C111-
    発行日: 2007/08/20
    公開日: 2017/10/02
    ジャーナル フリー
  • Eita FUJISHIMA, Kenji NAKASHIMA, Saneyasu YAMAGUCHI
    IEICE Transactions on Information and Systems
    2018年 E101.D 巻 2 号 415-427
    発行日: 2018/02/01
    公開日: 2018/02/01
    ジャーナル フリー

    Hadoop is a popular open-source MapReduce implementation. In the cases of jobs, wherein huge scale of output files of all relevant Map tasks are transmitted into Reduce tasks, such as TeraSort, the Reduce tasks are the bottleneck tasks and are I/O bounded for processing many large output files. In most cases, including TeraSort, the intermediate data, which include the output files of the Map tasks, are large and accessed sequentially. For improving the performance of these jobs, it is important to increase the sequential access performance. In this paper, we propose methods for improving the performance of Reduce tasks of such jobs by considering the following two things. One is that these files are accessed sequentially on an HDD, and the other is that each zone in an HDD has different sequential I/O performance. The proposed methods control the location to store intermediate data by modifying block bitmap of filesystem, which manages utilization (free or used) of blocks in an HDD. In addition, we propose striping layout for applying these methods for virtualized environment using image files. We then present performance evaluation of the proposed method and demonstrate that our methods improve the Hadoop application performance.

  • Makoto NAKAGAMI, Jose A.B. FORTES, Saneyasu YAMAGUCHI
    IEICE Transactions on Information and Systems
    2020年 E103.D 巻 10 号 2083-2093
    発行日: 2020/10/01
    公開日: 2020/10/01
    ジャーナル フリー

    Hadoop is a popular data-analytics platform based on Google's MapReduce programming model. Hard-disk drives (HDDs) are generally used in big-data analysis, and the effectiveness of the Hadoop platform can be optimized by enhancing its I/O performance. HDD performance varies depending on whether the data are stored in the inner or outer disk zones. This paper proposes a method that utilizes the knowledge of job characteristics to realize efficient data storage in HDDs, which in turn, helps improve Hadoop performance. Per the proposed method, job files that need to be frequently accessed are stored in outer disk tracks which are capable of facilitating sequential-access speeds that are higher than those provided by inner tracks. Thus, the proposed method stores temporary and permanent files in the outer and inner zones, respectively, thereby facilitating fast access to frequently required data. Results of performance evaluation demonstrate that the proposed method improves Hadoop performance by 15.4% when compared to normal cases when file placement is not used. Additionally, the proposed method outperforms a previously proposed placement approach by 11.1%.

  • Lixin WANG, Yutong LU, Wei ZHANG, Yan LEI
    IEICE Transactions on Information and Systems
    2016年 E99.D 巻 12 号 3035-3046
    発行日: 2016/12/01
    公開日: 2016/12/01
    ジャーナル フリー

    File system workloads are increasing write-heavy. The growing capacity of RAM in modern nodes allows many reads to be satisfied from memory while writes must be persisted to disk. Today's sophisticated local file systems like Ext4, XFS and Btrfs optimize for reads but suffer from workloads dominated by microdata (including metadata and tiny files). In this paper we present an LSM-tree-based file system, RFS, which aims to take advantages of the write optimization of LSM-tree to provide enhanced microdata performance, while offering matching performance for large files. RFS incrementally partitions the namespace into several metadata columns on a per-directory basis, preserving disk locality for directories and reducing the write amplification of LSM-trees. A write-ordered log-structured layout is used to store small files efficiently, rather than embedding the contents of small files into inodes. We also propose an optimization of global bloom filters for efficient point lookups. Experiments show our library version of RFS can handle microwrite-intensive workloads 2-10 times faster than existing solutions such as Ext4, Btrfs and XFS.

  • Yoshiko Yasuda, Shinichi Kawamoto, Atsushi Ebata, Jun Okitsu, Tatsuo Higuchi, Naoki Hamanaka
    IPSJ Digital Courier
    2005年 1 巻 1-14
    発行日: 2005年
    公開日: 2005/01/12
    ジャーナル フリー
    RX-NAS (Replicated eXpandable Network-Attached Storage), a scalable, reliable clustered NAS system designed for entry-level NAS, has been developed. RX-NAS is based on X-NAS, which is a simple clustered NAS architecture for entry-level NAS, and improves the reliability of X-NAS by adding new sets of X-NASs to the original one. The core feature of RX-NAS, namely on-line replication, replicates original file objects to new sets of X-NASs for each file block in real-time without changing clients' environments. RX-NAS has other key features for maintaining the manageability of entry-level NAS; namely, new synchronization and resynchronization functions can easily replicate original files and directories to other X-NAS systems completely or partially without changing clients' environments. In addition, its health-check function can eliminate a limitation on the configuration of RX-NAS and detect and report errors that occur in the RX-NAS system. To validate the RX-NAS concept, an RX-NAS prototype was designed and tested according to the NFSv3 implementation. These tests show that the RX-NAS improves system reliability while maintaining 80% of the throughput of X-NAS.
  • Dongyang ZHAN, Lin YE, Binxing FANG, Xiaojiang DU, Zhikai XU
    IEICE Transactions on Information and Systems
    2017年 E100.D 巻 10 号 2307-2318
    発行日: 2017/10/01
    公開日: 2017/10/01
    ジャーナル フリー

    Protecting critical files in operating system is very important to system security. With the increasing adoption of Virtual Machine Introspection (VMI), designing VMI-based monitoring tools become a preferential choice with promising features, such as isolation, stealthiness and quick recovery from crash. However, these tools inevitably introduce high overhead due to their operation-based characteristic. Specifically, they need to intercept some file operations to monitor critical files once the operations are executed, regardless of whether the files are critical or not. It is known that file operation is high-frequency, so operation-based methods often result in performance degradation seriously. Thus, in this paper we present CFWatcher, a target-based real-time monitoring solution to protect critical files by leveraging VMI techniques. As a target-based scheme, CFWatcher constraints the monitoring into the operations that are accessing target files defined by users. Consequently, the overhead depends on the frequency of target files being accessed instead of the whole filesystem, which dramatically reduces the overhead. To validate our solution, a prototype system is built on Xen with full virtualization, which not only is able to monitor both Linux and Windows virtual machines, but also can take actions to prevent unauthorized access according to predefined policies. Through extensive evaluations, the experimental results demonstrate that the overhead introduced by CFWatcher is acceptable. Especially, the overhead is very low in the case of a few target files.

  • ヘルマン ミハエル, 谷 正彦, 阪井 清美
    映像情報メディア学会技術報告
    1999年 23.41 巻 IPU99-44/IDY99-216
    発行日: 1999/06/25
    公開日: 2017/06/23
    会議録・要旨集 フリー
    テラヘルツ時間分解分光イメージングを撮る場合に、試料の各ピクセルでテラヘルツパルスの波形を記録する。これらのデータを集めたものは時間のインデックスをつけたテラヘルツイメージ、言い換えるとテラヘルツムービーである。このテラヘルツムービーは色々なアルゴリズム又はディスプレイモードで表示してマッピング出来る。我々は各々のディスプレイモードが、試料の物理的性質を如何にマッピング出来るかを説明し、又、如何に試料の違いを区別出来るかについても述べる。
  • Takeshi Yoshimura, Hiroshi Yamada, Kenji Kono
    Information and Media Technologies
    2013年 8 巻 3 号 655-664
    発行日: 2013年
    公開日: 2013/09/15
    ジャーナル フリー
    Operating systems (OSes) are crucial for achieving high availability of computer systems. Even if applications running on an operating system are highly available, a bug inside the kernel may result in a failure of the entire software stack. The objective of this study is to gain some insight into the development of the Linux kernel that is more resilient against software faults. In particular, this paper investigates the scope of error propagation. The propagation scope is process-local if the erroneous value is not propagated outside the process context that activated it. The scope is kernel-global if the erroneous value is propagated outside the process context that activated it. The investigation of the scope of error propagation gives us some insight into 1) defensive coding style, 2) reboot-less rejuvenation, and 3) general recovery mechanisms of the Linux kernel. For example, if most errors are process-local, we can rejuvenate the kernel without reboots because the kernel can be recovered simply by killing faulty processes. To investigate the scope of error propagation, we conduct an experimental campaign of fault injection on Linux 2.6.18, using a kernel-level fault injector widely used in the OS community. Our findings are (1) our target kernel (Linux 2.6.18) is coded defensively. This defensive coding style contributes to lower rates of error manifestation and kernel-global errors, (2) the scope of error propagation is mostly process-local in Linux, and (3) global propagation occurs with low probability. Even if an error corrupts a global data structure, other processes merely access to them.
  • Takeshi Yoshimura, Hiroshi Yamada, Kenji Kono
    IPSJ Online Transactions
    2013年 6 巻 55-64
    発行日: 2013年
    公開日: 2013/04/24
    ジャーナル フリー
    Operating systems (OSes) are crucial for achieving high availability of computer systems. Even if applications running on an operating system are highly available, a bug inside the kernel may result in a failure of the entire software stack. The objective of this study is to gain some insight into the development of the Linux kernel that is more resilient against software faults. In particular, this paper investigates the scope of error propagation. The propagation scope is process-local if the erroneous value is not propagated outside the process context that activated it. The scope is kernel-global if the erroneous value is propagated outside the process context that activated it. The investigation of the scope of error propagation gives us some insight into 1) defensive coding style, 2) reboot-less rejuvenation, and 3) general recovery mechanisms of the Linux kernel. For example, if most errors are process-local, we can rejuvenate the kernel without reboots because the kernel can be recovered simply by killing faulty processes. To investigate the scope of error propagation, we conduct an experimental campaign of fault injection on Linux 2.6.18, using a kernel-level fault injector widely used in the OS community. Our findings are (1) our target kernel (Linux 2.6.18) is coded defensively. This defensive coding style contributes to lower rates of error manifestation and kernel-global errors, (2) the scope of error propagation is mostly process-local in Linux, and (3) global propagation occurs with low probability. Even if an error corrupts a global data structure, other processes merely access to them.
  • 植物学雑誌
    1890年 4 巻 43 号 351-353
    発行日: 1890年
    公開日: 2019/10/17
    ジャーナル フリー
  • T. H. Thomas
    植物化学調節学会 研究発表記録集
    1990年 25 巻 1-2
    発行日: 1990/10/08
    公開日: 2018/02/15
    ジャーナル フリー
  • Fuyumasa Takatsu, Kohei Hiraga, Osamu Tatebe
    Journal of Information Processing
    2017年 25 巻 438-447
    発行日: 2017年
    公開日: 2017/06/15
    ジャーナル フリー

    The fusion of the research field of high-performance computing (HPC) with that of big data, which has become known as the field of extreme big data, is problematic in that file creation in storage systems such as distributed file systems is not optimized. That is, the large workload leads to simultaneous creations of many files by many processes when creating checkpoints. The need to improve the file creation processes prompted us to design a scale-out distributed file system for post-petascale systems named PPFS. PPFS consists of PPMDS, which is a scale-out distributed metadata server, and PPOSS, which is a scalable distributed storage server for flash storage. The high file creation performance of PPMDS was achieved by using a key-value store for metadata storage and non-blocking distributed transactions to update multiple entries simultaneously. PPOSS depends on PPOST, which is an object storage system that manages the underlying low-level storage, such as Fusion IO ioDrive, a flash device connected through PCI express supporting OpenNVM. The high file creation performance was attained by implementing the PPFS prototype using file creation optimization, termed bulk creation, to reduce the amount of communication between PPMDS and PPOSS. And, to enhance the I/O performance of PPOSS when the client process and PPOSS run on the same node, PPOSS accesses a local storage device directly. The prototype implementation of PPFS with a further file creation optimization called object prefetching achieves 138, 000 Operations Per Second for file creation when using five metadata servers and 128 client processes, thereby exceeding the performance of IndexFS by 2.52 times. With local access optimization, PPOSS reached its limit at a block size of 16KiB, which is an improvement of 1.5 times compared to before optimization. Furthermore, this evaluation indicates that PPFS has a good scalability on file creation and IO performance, that is required for post-petascale systems.

  • Takenori Atsumi, Toshihiro Arisaka, Toshihiko Shimizu, Takashi Yamaguchi
    The Proceedings of the International Conference on Motion and Vibration Control
    2002年 6.1 巻
    発行日: 2002年
    公開日: 2017/06/19
    会議録・要旨集 フリー
    We developed a design method that can suppress the vibration from high-order resonant modes in a head-positioning system of a hard disk drive. We used the vector locus of an open-loop transfer function to design both the controller and the structure simultaneously. Application of the method to an actual hard disk drive showed that positioning accuracy under high-order resonant modes can be improved by 55%. In addition, when all resonances are in-phase, the developed method can suppress vibrations caused by all mechanical resonances. We concluded that the method can design a control system with high robustness and good following control performance.
  • Nobunori Kami-ike, Tohru Minamino, Yong-Suk Che, Keiichi Namba
    生物物理
    2006年 46 巻 supplement2 号 S211-
    発行日: 2006/10/01
    公開日: 2017/05/01
    ジャーナル フリー
  • Ichiro Amitani, Ronald J. Baskin, Stephen C. Kowalczykowski
    生物物理
    2006年 46 巻 supplement2 号 S211-
    発行日: 2006/10/01
    公開日: 2017/05/01
    ジャーナル フリー
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