• 제목/요약/키워드: FTL

검색결과 166건 처리시간 0.022초

Fault Tolerant FTL Gaits for Walking over Irregular Terrain (비평탄 지형 보행을 위한 내고장성 FTL 걸음새)

  • Yang Jung-Min
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • 제43권3호
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    • pp.16-24
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    • 2006
  • In this paper, fault-tolerant gait planning of a hexapod robot for walking over irregular terrain is presented. The failure concerned in this paper is a locked joint failure for which a joint in a leg cannot move and is locked in place. Based on the previously proposed fault-tolerant tripod gait for walking over even terrain, fault-tolerant follow-the-leader(FTL) gaits are proposed for a hexapod robot with a failed leg to be able to walk over two-dimensional rough terrain, maintaining static stability and fault tolerance. The proposed FTL gait can have maximum stride length for a given foot position of a failed leg, and yields better ditch crossing ability than the previously developed gaits. The applicability of the proposed FTL gait is verified by using computer graphics simulations.

Performance Analysis of Flash Translation Layer using TPC-C Benchmark (플래시 변환 계층에 대한 TPC-C 벤치마크를 통한 성능분석)

  • Park, Sung-Hwan;Jang, Ju-Yeon;Suh, Young-Ju;Park, Won-Joo;Park, Sang-Won
    • Journal of KIISE:Computing Practices and Letters
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    • 제14권2호
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    • pp.201-205
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    • 2008
  • The flash memory is widely used as a main storage of embedded devices. It is adopted as a storage of database as growing the capacity of the flash memory. We run TPC-C benchmark on various FTL algorithms. But, the database shows poor performance on flash memory because the characteristic of I/O requests is full random. In this paper, we show the performance of all existing FTL algorithms is very poor. Especially, the FTL algorithm known as good at small mobile equipment shows worst performance. In addition, the chip-inter leaving which is a technique to improve the performance of the flash memory doesn't work well. In this paper, we inform you the reason that we need a new FTL algorithm and the direction for the database in the future.

Analysis and Advice on Cache Algorithms of SSD FTL (SSD FTL 캐시 알고리즘 분석 및 제언)

  • Hyung Bong, Lee;Tae Yun, Chung
    • KIPS Transactions on Computer and Communication Systems
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    • 제12권1호
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    • pp.1-8
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    • 2023
  • It is impossible to overwrite on an already allocated page in SSDs, so whenever a write operation occurs a page replacement with a clean page is required. To resolve this problem, SSDs have an internal flash translation layer called FTL that maps logical pages managed by a file system of operating system to currently allocated physical pages. SSD pages discarded due to write operations must be recycled through initialization, but since the number of initialization times is limited the FTL provides a caching function to reduce the number of writes in addition to the page mapping function, which is a core function. In this study, we focus on the FTL cache methodologies reducing the number of page writes and analyze the related algorithms, and propose a write-only cache strategy. As a result of experimenting with the write-only cache using a simulator, it showed an improvement of up to 29%.

An Efficient System Software of Flash Translation Layer for Large Block Flash Memory (대용량 플래시 메모리를 위한 효율적인 플래시 변환 계층 시스템 소프트웨어)

  • Chung Tae-Sun;Park Dong-Joo;Cho Sehyeong
    • The KIPS Transactions:PartA
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    • 제12A권7호
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    • pp.621-626
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    • 2005
  • Recently, flash memory is widely used in various embedded applications since it has many advantages in terms of non-volatility, fast access speed, shock resistance, and low power consumption. However, it requires a software layer called FTL(Flash Translation Layer) due to its hardware characteristics. We present a new FTL algorithm named LSTAFF(Large State Transition Applied Fast flash Translation Layer) which is designed for large block flash memory The presented LSTAFF is adjusted to flash memory with pages which are larger than operating system data sector sizes and we provide performance results based on our implementation of LSTAFF and previous FTL algorithms using a flash simulator.

FlaSim: A FTL Emulator using Linux Kernel Modules (FlaSim: 리눅스 커널 모듈을 이용한 FTL 에뮬레이터)

  • Choe, Hwa-Young;Kim, Sang-Hyun;Lee, Seoung-Won;Park, Sang-Won
    • Journal of KIISE:Computing Practices and Letters
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    • 제15권11호
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    • pp.836-840
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    • 2009
  • Many researchers have studied flash memory in order to replace hard disk storages. Many FTL algorithms have been proposed to overcome physical constraints of flash memory such as erase-before-write, wear leveling, and poor write performance. Therefore, these constraints should be considered for testing FTL algorithms and the performance evaluation of flash memory. As doing the experiments, we suffer from several problems with costs and settings in experimental configuration. When we, for example, replay the traces of Oracle to evaluate the I/O performance with flash memory, it is hard to extract exact traces of I/O operations in Oracle. Since there are only write operations in the log, it is impossible to gather read operations. In MySQL and SQLite, we can gather the read operations by changing I/O functions in the source codes. But it is not easy to search for the exact points about I/O and even if we can find out the points, we might get wrong results depending on how we modify source codes to get I/O traces. The FlaSim proposed in this paper removes the difficulties when we evaluate the performance of FTL algorithms and flash memory. Our Linux drivers emulate the flash memory as a hard disk. And we can easily obtain the usage statistics of flash memory such as the number of write, read, and erase operations. The FlaSim can be gracefully extended to support the additional modules implemented by novel algorithms and ideas. In this paper, we describe the structure of FTL emulator, development tools and operating methods. We expect this emulator to be helpful for many experiments and research with flash memory.

EAST: An Efficient and Advanced Space-management Technique for Flash Memory using Reallocation Blocks (재할당 블록을 이용한 플래시 메모리를 위한 효율적인 공간 관리 기법)

  • Kwon, Se-Jin;Chung, Tae-Sun
    • Journal of KIISE:Computing Practices and Letters
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    • 제13권7호
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    • pp.476-487
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    • 2007
  • Flash memory offers attractive features, such as non-volatile, shock resistance, fast access, and low power consumption for data storage. However, it has one main drawback of requiring an erase before updating the contents. Furthermore, flash memory can only be erased limited number of times. To overcome limitations, flash memory needs a software layer called flash translation layer (FTL). The basic function of FTL is to translate the logical address from the file system like file allocation table (FAT) to the physical address in flash memory. In this paper, a new FTL algorithm called an efficient and advanced space-management technique (EAST) is proposed. EAST improves the performance by optimizing the number of log blocks, by applying the state transition, and by using reallocation blocks. The results of experiments show that EAST outperforms FAST, which is an enhanced log block scheme, particularly when the usage of flash memory is not full.

The Construction Work Completion of the Fuel Test Loop (핵연료 노내조사시험설비 설치공사 완료)

  • Park, Kook-Nam;Lee, Chung-Young;Chi, Dae-Young;Park, Su-Ki;Shim, Bong-Sik;Ahn, Sung-Ho;Kim, Hark-Rho;Lee, Jong-Min
    • Proceedings of the KSME Conference
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    • 대한기계학회 2007년도 춘계학술대회A
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    • pp.291-295
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    • 2007
  • FTL(Fuel Test Loop) is a facility that confirms performance of nuclear fuel at a similar irradiation condition with that of nuclear power plant. FTL consists of In-Pile Test Section (IPS) and Out-Pile System (OPS). FTL construction work began on August, 2006 and ended on March, 2007. During Construction, ensuring the worker's safety was the top priority and installation of the FTL without hampering the integrity of the HANARO was the next one. Task Force Team was organized to do a construction systematically and the communication between members of the task force team was done through the CoP(community of Practice) notice board provided by the Institute. The installation works were done successfully overcoming the difficulties such as on the limited space, on the radiation hazard inside the reactor pool, and finally on the shortening of the shut down period of the HANARO. Without a sweet of the workers of the participating company of HEC(Hyundae Engineering Co, Ltd), HDEC(HyunDai Engineering & Construction Co. Ltd), equipment manufacturer, and the task force team, it is not possible to install the FTL facility within the planned shutdown period. The Commissioning of the FTL is on due to check the function and the performance of the equipment and the overall system as well. The FTL shall start operation with high burn up test fuels in early 2008 if the commissioning and licensing progress on schedule.

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The Effect of Absorbing Hot Write References on FTLs for Flash Storage Supporting High Data Integrity (데이터 무결성을 보장하는 플래시 저장 장치에서 잦은 쓰기 참조 흡수가 플래시 변환 계층에 미치는 영향)

  • Shim, Myoung-Sub;Doh, In-Hwan;Moon, Young-Je;Lee, Hyo-J.;Choi, Jong-Moo;Lee, Dong-Hee;Noh, Sam-H.
    • Journal of KIISE:Computing Practices and Letters
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    • 제16권3호
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    • pp.336-340
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    • 2010
  • Flash storages are prevalent as portable storage in computing systems. When we consider the detachability of Flash storage devices, data integrity becomes an important issue. To assure extreme data integrity, file systems synchronously write all file data to storage accompanying hot write references. In this study, we concentrate on the effect of hot write references on Flash storage, and we consider the effect of absorbing the hot write references via nonvolatile write cache on the performance of the FTL schemes in Flash storage. In 80 doing, we quantify the performance of typical FTL schemes for workloads that contain hot write references through a wide range of experiments on a real system environment. Through the results, we conclude that the impact of the underlying FTL schemes on the performance of Flash storage is dramatically reduced by absorbing the hot write references via nonvolatile write cache.

Efficiently Managing the B-tree using Write Pattern Conversion on NAND Flash Memory (낸드 플래시 메모리 상에서 쓰기 패턴 변환을 통한 효율적인 B-트리 관리)

  • Park, Bong-Joo;Choi, Hae-Gi
    • Journal of KIISE:Computer Systems and Theory
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    • 제36권6호
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    • pp.521-531
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    • 2009
  • Flash memory has physical characteristics different from hard disk where two costs of a read and write operations differ each other and an overwrite on flash memory is impossible to be done. In order to solve these restrictions with software, storage systems equipped with flash memory deploy FTL(Flash Translation Layer) software. Several FTL algorithms have been suggested so far and most of them prefer sequential write pattern to random write pattern. In this paper, we provide a new technique to efficiently store and maintain the B-tree index on flash memory. The operations like inserts, deletes, updates of keys for the B-tree generate random writes rather than sequential writes on flash memory, leading to inefficiency to the B-tree maintenance. In our technique, we convert random writes generated by the B-tree into sequential writes and then store them to the write-buffer on flash memory. If the buffer is full later, some sequential writes in the buffer will be issued to FTL. Our diverse experimental results show that our technique outperforms the existing ones with respect to the I/O cost of flash memory.

Design and Implementation of Flash Translation Layer with O(1) Crash Recovery Time (O(1) 크래시 복구 수행시간을 갖는 FTL의 설계와 구현)

  • Park, Joon Young;Park, Hyunchan;Yoo, Chuck
    • KIISE Transactions on Computing Practices
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    • 제21권10호
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    • pp.639-644
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    • 2015
  • The capacity of flash-based storage such as Solid State Drive(SSD) and embedded Multi Media Card(eMMC) is ever-increasing because of the needs from the end-users. However, if a flash-based storage crashes, such as during power failure, the flash translation layer(FTL) is responsible for the crash recovery based on the entire flash memory. The recovery time increases as the capacity of the flash-based storages increases. We propose O1FTL with O(1) crash recovery time that is independent of the flash capacity. O1FTL adopts the working area technique suggested for the flash file system and evaluates the design on a real hardware platform. The results show that O1FTL achieves a crash recovery time that is independent of the capacity and the overhead, in terms of I/O performance, and achieves a low P/E cycle.