• Title, Summary, Keyword: FTL

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Flash Translation Layer for Heterogeneous NAND Flash-based Storage Devices Based on Access Patterns of Logical Blocks (논리 블록의 접근경향을 활용한 이종 낸드 플래시 기반 저장장치를 위한 Flash Translation Layer)

  • Bang, Kwanhu;Park, Sang-Hoon;Lee, Hyuk-Jun;Chung, Eui-Young
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.5
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    • pp.94-101
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    • 2013
  • The market for NAND flash-based storage devices has grown significantly as they rapidly replace traditional disk-based storage devices. Heterogeneous NAND flash-based storage devices using both multi-level cell (MLC) and single-level cell (SLC) NAND flash memories are also actively researched since both types of memories complement each other. Heterogeneous NAND flash-based storage devices suffer from the overheads incurred by migration from SLC to MLC and garbage collection of SLC. This paper proposes a new flash translation layer (FTL) for heterogeneous NAND flash-based storage devices to reduce the overheads by utilizing SLC efficiently. The proposed FTL analyzes the access patterns of logical blocks and selects and stores only logical blocks expected to bring performance improvement in SLC. The experimental results show that the total execution time of heterogeneous NAND flash-based storage devices with our proposed FTL scheme is 35% shorter than that with the previously proposed best FTL scheme.

FAST : A Log Buffer Scheme with Fully Associative Sector Translation for Efficient FTL in Flash Memory (FAST :플래시 메모리 FTL을 위한 완전연관섹터변환에 기반한 로그 버퍼 기법)

  • Park Dong-Joo;Choi Won-Kyung;Lee Sang-Won
    • The KIPS Transactions:PartA
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    • v.12A no.3
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    • pp.205-214
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    • 2005
  • Flash memory is at high speed used as storage of personal information utilities, ubiquitous computing environments, mobile phones, electronic goods, etc. This is because flash memory has the characteristics of low electronic power, non-volatile storage, high performance, physical stability, portability, and so on. However, differently from hard disks, it has a weak point that overwrites on already written block of flash memory is impossible to be done. In order to make an overwrite possible, an erase operation on the written block should be performed before the overwrite, which lowers the performance of flash memory highly. In order to solve this problem the flash memory controller maintains a system software module called the flash translation layer(FTL). Of many proposed FTL schemes, the log block buffer scheme is best known so far. This scheme uses a small number of log blocks of flash memory as a write buffer, which reduces the number of erase operations by overwrites, leading to good performance. However, this scheme shows a weakness of low page usability of log blocks. In this paper, we propose an enhanced log block buffer scheme, FAST(Full Associative Sector Translation), which improves the page usability of each log block by fully associating sectors to be written by overwrites to the entire log blocks. We also show that our FAST scheme outperforms the log block buffer scheme.

A File Recovery Technique for Digital Forensics on NAND Flash Memory (NAND 플래시 메모리에서 디지털 포렌식을 위한 파일 복구기법)

  • Shin, Myung-Sub;Park, Dong-Joo
    • Journal of KIISE:Databases
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    • v.37 no.6
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    • pp.292-299
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    • 2010
  • Recently, as flash memory is used as digital storage devices, necessity for digital forensics is growing in a flash memory area for digital evidence analysis. For this purpose, it is important to recover crashed files stored on flash memory efficiently. However, it is inefficient to apply the hard disk based file recovery techniques to flash memory, since hard disk and flash memory have different characteristics, especially flash memory being unable to in-place update. In this paper, we propose a flash-aware file recovery technique for digital forensics. First, we propose an efficient search technique to find all crashed files. This uses meta-data maintained by FTL(Flash Translation Layer) which is responsible for write operation in flash memory. Second, we advise an efficient recovery technique to recover a crashed file which uses data location information of the mapping table in FTL. Through diverse experiments, we show that our file recovery technique outperforms the hard disk based technique.

Log Buffer Management Scheme for NAND Flash Memory in Real-Time Systems (실시간 시스템용 낸드 플래시 메모리를 위한 로그 버퍼 관리 기법)

  • Cho, Hyun-Jin;Ha, Byung-Min;Shin, Dong-Kun;Eom, Young-Ik
    • Journal of KIISE:Computer Systems and Theory
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    • v.36 no.6
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    • pp.463-475
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    • 2009
  • Flash memory is suitable for real time systems because of its consistent performance for random access, low power consumption and shock resistance. However, flash memory needs blocking time to perform a garbage collection to reclaim invalidated pages. Moreover, the worst-case garbage collection time is significantly longer than the best-case garbage collection time. In this paper, we propose a FTL (Flash Translation Layer) mapping scheme called KAST (K-Associative Sector Translation). In the KAST scheme, user can control the maximum association of the log block to limit the worst-case garbage collection time. Performance evaluation using simulation shows that not only KAST completes the garbage collection within the specified time but also provides about 10~15% better average performance than existing FTL schemes.

Development of Performance Analysis Tool for Flash Disk on Windows Platform (윈도우즈 기반 플래시 디스크의 성능 분석을 위한 도구 개발)

  • Park Sung-Hwan;Yoo Hyun-Seok;Kim Do Yun;Park Won-Joo;Oh Kisun;Lee Sang-Won;Park Sangwon
    • Proceedings of the Korean Information Science Society Conference
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    • pp.826-828
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    • 2005
  • 이동 기기의 저장 장치로 플래시 메모리가 널리 사용되고 있으며 고정 하드 디스크를 대체하는 저장 매제로 부상하고 있다. 그러므로 플래시 메모리의 특성을 잘 이해하고, 최대한 효율적으로 플래시 메모리를 사용할 필요성이 있다. 이러한 역할을 해주는 것은 플래시 내부의 시스템 소프트웨어인 FTL(Fiash Translation Layer)이다. FTL은 운영체제가 디스크에 전달하는 블록을 물리적인 플래시 메모리에 맵핑하는 역할을 한다. 그러므로 플래시 메모리의 성능은 FTL 알고리즘이 결정한다. 플래시를 대체한 플래시 디스크에서는 기존의 파일 시스템이 탑재되며 간단한 섹터 기반외 이동형 기기에서와는 다른 특성을 가진다. FTL 성능을 평가하기 위해서는 실제적으로 플래시 메모리가 장착된 제품들이 동작하는 시스템에서 실험을 해야 한다. 많은 플래시 디스크는 윈도우즈에서 동작하므로 윈도우즈의 디스크 I/O를 추출하여 실험을 해야만 한다. 본 논문에서는 윈도우즈에서 물리적인 디스크 I/O 패턴을 추출하여 FTL 알고리즘의 성능을 평가하기 위한 도구 개발에 대하여 설명하고 이에 대한 간단한 결과를 보인다.

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Robustness Analysis of Flash Memory Software using Fault Injection Tests (폴트 삽입 테스트를 이용한 플래시 메모리 소프트웨어의 강건성 분석)

  • Lee, Dong-Hee
    • 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.

THE FAST TRUNCATED LAGRANGE METHOD FOR IMAGE DEBLURRING WITH ANTIREFLECTIVE BOUNDARY CONDITIONS

  • Oh, SeYoung;Kwon, SunJoo
    • Journal of the Chungcheong Mathematical Society
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    • v.31 no.1
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    • pp.137-149
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    • 2018
  • In this paper, under the assumption of the symmetry point spread function, antireflective boundary conditions(AR-BCs) are considered in connection with the fast truncated Lagrange(FTL) method. The FTL method is proposed as an image restoration method for large-scale ill-conditioned BTTB(block Toeplitz with Toeplitz block) and BTHHTB(block Toeplitz-plus-Hankel matrix with Toeplitz-plus-Hankel blocks) linear systems([13, 17]). The implementation and efficiency of the FTL method in the AR-BCs are further illustrated. Especially, by employing the AR-BCs, both the continuity of the image and the continuity of its normal derivative are preserved at the boundary. A reconstructed image with less artifacts at the boundary is obtained as a result.

Design of NAND Flash Translation Layer Based on Valid Page Lookup Table (유효 페이지 색인 테이블을 활용한 NAND Flash Translation Layer 설계)

  • 신정환;이인환
    • Proceedings of the IEEK Conference
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    • pp.15-18
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    • 2003
  • Flash memory becomes more important for its fast access speed, low-power, shock resistance and nonvolatile storage. But its native restrictions that have limited 1ifetime, inability of update in place, different size unit of read/write and erase operations need to managed by FTL(Flash Translation Layer). FTL has to control the wear-leveling, address mapping, bad block management of flash memory. In this paper, we focuses on the fast access to address mapping table and proposed the way of faster valid page search in the flash memory using the VPLT(Valid Page Lookup Table). This method is expected to decrease the frequency of access of flash memory that have an significant effect on performance of read and block-transfer operations. For the validations, we implemented the FTL based on Windows CE platform and obtained an improved result.

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Implementation of I/O Trace Visualization Tool for Flash Memory based Storage Systems (플래시메모리 기반 저장시스템의 성능 분석을 위한 I/O 트레이스 가시화 도구 개발)

  • Yoon, Kyeong-Hoon;Jung, Ho-Young;Park, Sung-Min;Cha, Jae-Hyuk;Kang, Soo-Yong
    • Proceedings of the Korean Information Science Society Conference
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    • pp.351-355
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    • 2006
  • 최근 플래시 메모리는 여러 장점들 때문에 다양한 휴대기기에서 많이 사용되고 있다. 반면 내구성에 약점을 갖고 있는 플래시 메모리의 특성 때문에 최대한 소거 동작을 적게 하여 오랫동안 사용하는 FTL 알고리즘을 개발하는 연구가 필요하다. 이러한 FTL 알고리즘을 실험하고 평가하기 위해서 트레이스 데이터를 연구에 활용하는 일이 많아지면서, 쉽게 트레이스 데이터에 대한 분석도구를 개발하였다. 우리는 트레이스 데이터를 다양한 그래프로 그려주고 통계치를 산출해주는 도구를 개발하였고, 이를 바탕으로 트레이스 분석 작업을 쉽게 할 수 있도록 하였다. 마찬가지로 이러한 도구는 버퍼 교체정책을 실험하고 평가하는 일에도 사용 될수 있다. 그리고 각 그래프를 설명하면서 트레이스에 데이터 대한 설명과 함께 분석을 통하여 버퍼교체 알고리즘 및 FTL 알고리즘에 어떻게 활용 할 수 있는지 설명하였다.

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