• Title, Summary, Keyword: FTL

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WAL-FTL: Designing an FTL that supports SQLite's WAL functionalities efficiently (WAL-FTL: SQLite 의 WAL 기능을 효율적으로 지원하는 FTL 설계 방안)

  • Lee, Doogie;Roh, Hongchan;Park, Sanghyun
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.688-691
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    • 2014
  • 스마트 기기에서는 NAND 기반 저장장치 위에 SQLite 를 활용하여 데이터를 관리하는 방식이 널리 쓰이고 있다. SQLite 에서 트랜잭션의 원소성을 보장하기 위한 기법인 WAL 은 트랜잭션 처리의 동시성을 높일 수 있어 다중 쓰레드 환경에 적합하지만, 오버헤드가 큰 체크포인트 동작을 주기적으로 수행하는 문제가 있다. 본 논문에서는 WAL 의 아이디어를 저장장치에 도입하여 트랜잭션을 처리할 때 동시성은 높이면서 오버헤드는 줄일 수 있는 저장장치 FTL 을 제안한다.

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An In-Depth Analysis and Improvement on Cache Mechanisms of SSD FTL (SSD FTL의 캐시 메커니즘에 대한 심층 분석 및 개선)

  • Lee, Hyung-Bong;Chung, Tae-Yun
    • IEMEK Journal of Embedded Systems and Applications
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    • v.15 no.1
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    • pp.9-16
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    • 2020
  • Recently, the capacity of SSD has been increasing rapidly due to the improvement of flash memory density. To take full advantage of these SSDs, first of all, FTL's prompt adaptation is necessary. The FTL is a translation layer existing in SSDs to overcome the drawback of the SSD that cannot be modified in place, and has garbage collection and caching functions in addition to the map table management function. In this study, we focus on caching function, compare and analyze the cache implementation methodologies, and propose improved methods. Typical cache implementations divide the cache into groups, manage and retrieve the caches in the group as a linked list. Thus, searches are made in the order of the linked list. In contrast, we propose a method of sequential searching using the search area group of a cache registered in the map table regardless of the linked list and cache group. Experimental results show that the proposed method has a 2.5 times improvement over the conventional method.

Efficient FTL Mapping Management for Multiple Sector Size-based Storage Systems with NAND Flash Memory (다중 섹터 사이즈를 지원하는 낸드 플래시 메모리 기반의 저장장치를 위한 효율적인 FTL 매핑 관리 기법)

  • Lim, Seung-Ho;Choi, Min
    • Journal of KIISE:Computing Practices and Letters
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    • v.16 no.12
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    • pp.1199-1203
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    • 2010
  • Data transfer between host system and storage device is based on the data unit called sector, which can be varied depending on computer systems. If NAND flash memory is used as a storage device, the variant sector size can affect storage system performance since its operation is much related to sector size and page size. In this paper, we propose an efficient FTL mapping management scheme to support multiple sector size within one NAND flash memory based storage device, and analyze the performance effect and management overhead. According to the proposed scheme, the management overhead of proposed FTL management is lower than conventional scheme when various sector sizes are configured in computer systems, while performance is less degraded in comparison with single sector size support system.

An Address Translation Technique Large NAND Flash Memory using Page Level Mapping (페이지 단위 매핑 기반 대용량 NAND플래시를 위한 주소변환기법)

  • Seo, Hyun-Min;Kwon, Oh-Hoon;Park, Jun-Seok;Koh, Kern
    • Journal of KIISE:Computing Practices and Letters
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    • v.16 no.3
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    • pp.371-375
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    • 2010
  • SSD is a storage medium based on NAND Flash memory. Because of its short latency, low power consumption, and resistance to shock, it's not only used in PC but also in server computers. Most SSDs use FTL to overcome the erase-before-overwrite characteristic of NAND flash. There are several types of FTL, but page mapped FTL shows better performance than others. But its usefulness is limited because of its large memory footprint for the mapping table. For example, 64MB memory space is required only for the mapping table for a 64GB MLC SSD. In this paper, we propose a novel caching scheme for the mapping table. By using the mapping-table-meta-data we construct a fully associative cache, and translate the address within O(1) time. The simulation results show more than 80 hit ratio with 32KB cache and 90% with 512KB cache. The overall memory footprint was only 1.9% of 64MB. The time overhead of cache miss was measured lower than 2% for most workload.

The Design Status of the Irradiation Facility for Fuel Test (핵연료 시험용 노내조사시험설비의 설계 현황)

  • Park, Kook-Nam;Sim, Bong-Shick;Ahn, Sung-Ho;Yoo, Seong-Yeon
    • Proceedings of the SAREK Conference
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    • pp.310-315
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    • 2007
  • The FTL has been developed to be able to irradiate test fuels at the irradiation hole(IR1 hole) by considering its utility and user's irradiation requirements. FTL consists of In-Pile Test Section (IPS) and Out-of-Pile System (OPS). Test condition in IPS such as pressure, temperature and the water quality, can be controlled by OPS. For safety assurance IPS is designed to have dual stainless steel pressure vessel and OPS is composed of main cooling water system, emergency cooling water system, LMP(letdown, make-up, purification) system, etc. FTL Conceptual design was set up in 2001, basic design had completed including a design requirement, basic piping & instrument diagram (P&ID), and the detail design in 2004. In 2005, the development team carried out purchase and manufacture hardware and make a contract for construction work. FTL construction work began on August, 2006 and ended on March, 2007. After FTL development which is expected to be finished by 2008, FTL will be used for the irradiation test of the new PWR-type fuel and can maximize the usage of HANARO.

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Design and Implementation of an Efficient FTL for Large Block Flash Memory using Improved Hybrid Mapping (향상된 혼합 사상기법을 이용한 효율적인 대블록 플래시 메모리 변환계층 설계 및 구현)

  • Park, Dong-Joo;Kwak, Kyoung-Hoon
    • Journal of KIISE:Computing Practices and Letters
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    • v.15 no.1
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    • pp.1-13
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    • 2009
  • Flash memory is widely used as a storage medium of mobile devices such as MP3 players, cellular phones and digital cameras due to its tiny size, low power consumption and shock resistant characteristics. Currently, there are many studies to replace HDD with flash memory because of its numerous strong points. To use flash memory as a storage medium, FTL(Flash Translation Layer) is required since flash memory has erase-before-write constraints and sizes of read/write unit and erase unit are different from each other. Recently, new type of flash memory called "large block flash memory" is introduced. The large block flash memory has different physical structure and characteristics from previous flash memory. So existing FTLs are not efficiently operated on large block flash memory. In this paper, we propose an efficient FTL for large block flash memory based on FAST(Fully Associative Sector Translation) scheme and page-level mapping on data blocks.

A File Clustering Algorithm for Wear-leveling (마모도 평준화를 위한 File Clustering 알고리즘)

  • Lee, Taehwa;Cha, Jaehyuk
    • Journal of Digital Contents Society
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    • v.14 no.1
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    • pp.51-57
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    • 2013
  • Storage device based on Flash Memory have many attractive features such as high performance, low power consumption, shock resistance, and low weight, so they replace HDDs to a certain extent. An Storage device based on Flash Memory has FTL(Flash Translation Layer) which emulate block storage devices like HDDs. A garbage collection, one of major functions of FTL, effects highly on the performance and the lifetime of devices. However, there is no de facto standard for new garbage collection algorithms. To solve this problem, we propose File Clustering Algorithm. File Clustering Algorithm respect to update page from same file at the same time. So, these are clustered to same block. For this mechanism, We propose Page Allocation Policy in FTL and use MIN-MAX GAP to guarantee wear leveling. To verify the algorithm in this paper, we use TPC Benchmark. So, The performance evaluation reveals that the proposed algorithm has comparable result with the existing algorithms(No wear leveling, Hot/Cold) and shows approximately 690% improvement in terms of the wear leveling.

SSR (Simple Sector Remapper) the fault tolerant FTL algorithm for NAND flash memory

  • Lee, Gui-Young;Kim, Bumsoo;Kim, Shin-han;Byungsoo Jung
    • Proceedings of the IEEK Conference
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    • pp.932-935
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    • 2002
  • In this paper, we introduce new FTL(Flash Translation Layer) driver algorithm that tolerate the power off errors. FTL driver is the software that provide the block device interface to the upper layer software such as file systems or application programs that using the flash memory as a block device interfaced storage. Usually, the flash memory is used as the storage devices of the mobile system due to its low power consumption and small form factor. In mobile system, the state of the power supplement is not stable, because it using the small sized battery that has limited capacity. So, a sudden power off failure can be occurred when we read or write the data on the flash memory. During the write operation, power off failure may introduce the incomplete write operation. Incomplete write operation denotes the inconsistency of the data in flash memory. To provide the stable storage facility with flash memory in mobile system, FTL should provide the fault tolerance against the power off failure. SSR (Simple Sector Remapper) is a fault tolerant FTL driver that provides block device interface and also provides tolerance against power off errors.

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Design of an Efficient FTL Algorithm Exploiting Locality Based on Sector-level Mapping (Locality를 이용한 섹터 매핑 기법의 효율적인 FTL 알고리듬)

  • Hong, Soo-Jin;Hwang, Sun-Young
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.7B
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    • pp.818-826
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    • 2011
  • This paper proposes a novel FTL (Flash Translation Layer) algorithm employing sector-level mapping technique based on locality to reduce the number of erase operations in flash memory accesses. Sector-level mapping technique shows higher performance than other mapping techniques, even if it requires a large mapping table. The proposed algorithm reduces the size of mapping table by employing dynamic table update, processes sequential writes by exploiting sequential locality and extracts hot sector in random writes. Experimental results show that the number of erase operations has been reduced by 75.4%, 65.8%, and 10.3% respectively when compared with well-known BAST, FAST and sector mapping algorithms.

A Multi-level Mapping Table Scheme for SSD (SSD를 위한 다단계 사상 테이블 기법)

  • Yang, Soo-Hyeon;Ryu, Yeonseung
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.1591-1594
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    • 2010
  • NAND 플래시 메모리 기반의 Solid State Disk (SSD)의 내부에는 Flash Translation Layer (FTL)이라는 소프트웨어가 사용되고 있다. FTL은 파일 시스템으로부터 요청되는 논리 주소를 플래시 메모리의 물리 주소로 변환하며 이를 위하여 사상 테이블을 사용한다. 사상 테이블의 빠른 접근을 위하여 사상 테이블은 SSD 내부의 RAM에 유지하는데 SSD의 용량이 커지게 되면 사상 테이블로 인해 요구되는 RAM의 크기도 커지는 문제점이 있다. 본 논문에서는 FTL의 사상 테이블을 페이지 단위로 나누어 필요할 때마다 RAM에 적재하는 다단계 사상 테이블 기법을 연구하였다.

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