• Title, Summary, Keyword: FTL

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Data De-duplication and Recycling Technique in SSD-based Storage System for Increasing De-duplication Rate and I/O Performance (SSD 기반 스토리지 시스템에서 중복률과 입출력 성능 향상을 위한 데이터 중복제거 및 재활용 기법)

  • Kim, Ju-Kyeong;Lee, Seung-Kyu;Kim, Deok-Hwan
    • Journal of the Institute of Electronics and Information Engineers
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    • v.49 no.12
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    • pp.149-155
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    • 2012
  • SSD is a storage device of having high-performance controller and cache buffer and consists of many NAND flash memories. Because NAND flash memory does not support in-place update, valid pages are invalidated when update and erase operations are issued in file system and then invalid pages are completely deleted via garbage collection. However, garbage collection performs many erase operations of long latency and then it reduces I/O performance and increases wear leveling in SSD. In this paper, we propose a new method of de-duplicating valid data and recycling invalid data. The method de-duplicates valid data and then recycles invalid data so that it improves de-duplication ratio. Due to reducing number of writes and garbage collection, the method could increase I/O performance and decrease wear leveling in SSD. Experimental result shows that it can reduce maximum 20% number of garbage collections and 9% I/O latency than those of general case.

High Performance Nand Flash Controller using Multi-Processing Scheme (고속 처리가 가능한 다중처리 Nand 플래시 Controller)

  • Kang, Shin-Wook;Lee, Dong-Woo;Jeong, Seong-Hun;Lee, Yong-Surk
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.46 no.1
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    • pp.7-14
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    • 2009
  • Lately, NAND flash cards have been used to store massive amounts of multimedia data. However, these nand flash cells itself has a slow operation time and by that, the nand flash cards are not appropriate for high performance massive data transfer. Indeed, most flash card products have a disadvantage in that they require plenty of time to transfer massive amounts of data. Therefore, we propose a new architectural design for the hardware and software of the NAND flash cards by improving their data transfer rate. Our design is based on a multiprocessing which is different from the conventional serial processing method. We simulated our design under the VIP (Virtual IP) environment, and verified our work using FPGA test platforms. As a result, the downloading performances was approximately 160MB/s on VIP and 85.3MB/s on FPGA.

qtar: Design and Implementation of an Optimized tar Command with FTL-level Remapping (qtar: 플래시 변환 계층 리매핑 기법을 이용한 최적화된 tar 명령어 구현)

  • Ryoo, Jeongseok;Hahn, Sangwook Shane;Kim, Jihong
    • Journal of KIISE
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    • v.45 no.1
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    • pp.9-14
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    • 2018
  • Tar is a Linux command that combines several files into a single file. Combining multiple small files into large files increases the compression efficiency and data transfer speed. However, tar has a problem in that smaller target files, result in a lower performance. In this paper, we show that this performance degradation occurs when tar reads the data from the target files and propose qtar (quick tar) to solve this problem via flash-level remapping. When the size of an I/O request is less than 1 MB, the I/O performance decreases proportionally to the decrease in size of the I/O request. Since tar reads the data of files one by one, a smaller file size results in a lower performance. Therefore, the remapping technique is implemented in qtar to read data from the target files at the maximum I/O size regardless of the size of each file. Our evaluations show that the execution time with qtar is reduced by up to 3.4 times compared to that with tar.

A Cross Layer Optimization Technique for Improving Performance of MLC NAND Flash-Based Storages (MLC 낸드 플래시 기반 저장장치의 쓰기 성능 개선을 위한 계층 교차적 최적화 기법)

  • Park, Jisung;Lee, Sungjin;Kim, Jihong
    • Journal of KIISE
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    • v.44 no.11
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    • pp.1130-1137
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    • 2017
  • The multi-leveling technique that stores multiple bits in a single memory cell has significantly improved the density of NAND flash memory along with shrinking processes. However, because of the side effects of the multi-leveling technique, the average write performance of MLC NAND flash memory is degraded more than twice that of SLC NAND flash memory. In this paper, we introduce existing cross-layer optimization techniques proposed to improve the performance of MLC NAND flash-based storages, and propose a new integration technique that overcomes the limitations of existing techniques by exploiting their complementarity. By fully exploiting the performance asymmetry in MLC NAND flash devices at the flash translation layer, the proposed technique can handle many write requests with the performance of SLC NAND flash devices, thus significantly improving the performance of NAND flash-based storages. Experimental results show that the proposed technique improves performance 39% on average over individual techniques.

Synthesis and Characterization of Polyamide Having Photoreactive Group in the Backbone and its Liquid Crystal Aligning Property (광반응성 작용기를 주사슬에 갖는 폴리아미드의 합성과 특성 분석 및 액정분자의 배향 특성)

  • Jung, Eun-Young;Lee, Tae-Jin;Lee, Seung-Woo
    • Polymer Korea
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    • v.35 no.4
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    • pp.350-355
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    • 2011
  • A soluble polyamide containing photosensitive l,4-phenylenediacrylic acid (PDA) in main chain with biphenyl moiety was synthesized. The chemical structure of synthesized polyamide was investigated by means of $^1H$ NMR spectroscopy. The polymer was stable up to $280^{\circ}C$ and soluble in organic solvents, giving a good quality of thin films. The photoreaction of unpolarized LTV irradiated films was investigated by means of UV-vis absorption spectroscopy and FTlR spectroscopy, and liquid crystals (LCs) alignment property was examined by exposing to linearly polarized UV light (LPUVL) of 260~380 nm. The polyamide in film has excellent photoreactivity to unpolarized UV light. Direction selective photoreaction of PDA moiety in Lhe film was found to further induce nematic liquid -crystals to align along a perpendicular direction with respect to the electric vector of LPUVL, regardless of exposure energy of LPUVL. In addition, pretilt angle was measured by means of crystal rotation method. LPUVL-exposed polymer film induced the alignment of liquid-crystals (LC) with a pretilt angle of 0.2~$0.5^{\circ}$.

Design and Implementation of B-Tree on Flash Memory (플래시 메모리 상에서 B-트리 설계 및 구현)

  • Nam, Jung-Hyun;Park, Dong-Joo
    • Journal of KIISE:Databases
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    • v.34 no.2
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    • pp.109-118
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    • 2007
  • Recently, flash memory is used to store data in mobile computing devices such as PDAs, SmartCards, mobile phones and MP3 players. These devices need index structures like the B-tree to efficiently support some operations like insertion, deletion and search. The BFTL(B-tree Flash Translation Layer) technique was first introduced which is for implementing the B-tree on flash memory. Flash memory has characteristics that a write operation is more costly than a read operation and an overwrite operation is impossible. Therefore, the BFTL method focuses on minimizing the number of write operations resulting from building the B-tree. However, we indicate in this paper that there are many rooms of improving the performance of the I/O cost in building the B-tree using this method and it is not practical since it increases highly the usage of the SRAM memory storage. In this paper, we propose a BOF(the B-tree On Flash memory) approach for implementing the B-tree on flash memory efficiently. The core of this approach is to store index units belonging to the same B-tree node to the same sector on flash memory in case of the replacement of the buffer used to build the B-tree. In this paper, we show that our BOF technique outperforms the BFTL or other techniques.

An Empirical Study on Linux I/O stack for the Lifetime of SSD Perspective (SSD 수명 관점에서 리눅스 I/O 스택에 대한 실험적 분석)

  • Jeong, Nam Ki;Han, Tae Hee
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.9
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    • pp.54-62
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    • 2015
  • Although NAND flash-based SSD (Solid-State Drive) provides superior performance in comparison to HDD (Hard Disk Drive), it has a major drawback in write endurance. As a result, the lifetime of SSD is determined by the workload and thus it becomes a big challenge in current technology trend of such as the shifting from SLC (Single Level Cell) to MLC (Multi Level cell) and even TLC (Triple Level Cell). Most previous studies have dealt with wear-leveling or improving SSD lifetime regarding hardware architecture. In this paper, we propose the optimal configuration of host I/O stack focusing on file system, I/O scheduler, and link power management using JEDEC enterprise workloads in terms of WAF (Write Amplification Factor) which represents the efficiency perspective of SSD life time especially for host write processing into flash memory. Experimental analysis shows that the optimum configuration of I/O stack for the perspective of SSD lifetime is MinPower-Dead-XFS which prolongs the lifetime of SSD approximately 2.6 times in comparison with MaxPower-Cfq-Ext4, the best performance combination. Though the performance was reduced by 13%, this contributions demonstrates a considerable aspect of SSD lifetime in relation to I/O stack optimization.

A Study on the Legal Proposal of Crew's Fatigue Management in the Aviation Regulations (항공법규에서의 승무원 피로관리기준 도입방안에 관한 연구 - ICAO, FAA, EASA 기준을 중심으로 -)

  • Lee, Koo-Hee;Hwang, Ho-Won
    • The Korean Journal of Air & Space Law and Policy
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    • v.27 no.1
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    • pp.29-73
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    • 2012
  • Aviation safety is the State and industry's top priority and more scientific approaches for fatigue management should be needed. There are lately various studies and regulation changes for crew fatigue management with ICAO, FAA and EASA. ICAO issued the provisions of fatigue management for flight crew since 1st edition, 1969, of Annex 6 operation of aircraft as a Standards and Recommended practice(SARPs). Unfortunately, there have been few changes and improvement to fatigue management provisions since the time they were first introduced. However the SARPs have been big changed lately. ICAO published guidance materials for development of prescriptive fatigue regulations through amendment 33A of Annex 6 Part 1 as applicable November 19th 2009. And then ICAO introduced additional amendment for using Fatigue Risk Management System (FRMS) with $35^{th}$ amendment in 2011. According to the Annex 6, the State of the operator shall establish a) regulations for flight time, flight duty period, duty period and rest period limitations and b) FRMS regulations. The Operator shall implement one of following 3 provisions a) flight time, flight duty period, duty period and rest period limitations within the prescriptive fatigue management regulations established by the State of the Operator; or b) a FRMS; or c) a combination of a) and b). U.S. FAA recently published several kinds of Advisory Circular about flightcrew fatigue. U.S. passed "Airline Safety and FAA Extension Act of 2010" into law on August 1st, 2010. This mandates all commercial air carriers to develop a FAA-acceptable Fatigue Risk Management Plan(FRMP) by October 31st, 2010. Also, on May 16, 2012, the FAA published a final rule(correction) entitled 'Flightcrew Member Duty and Rest Requirements; correction to amend its existing prescriptive regulations. The new requirements are required to implement same regulations for domestic, flag and supplemental operations from January 4, 2014. EASA introduced a Notice of Proposed Amendment (NPA) 2010-14 entitled "Draft opinion of the European Aviation Safety Agency for a Commission Regulation establishing the implementing rules on Flight and Duty Time Limitations and Rest Requirements for Commercial Air Transport with aeroplanes" on December 10, 2010. The purpose of this NPA is to develop and implement fatigue management for commercial air transport operations. Comparing with Korean and foreign regulations regarding fatigue management, the provisions of ICAO, FAA, EASA are more considering various fatigue factors and conditions. Korea regulations should be needed for some development of insufficiency points. In this thesis, I present the results of the comparative study between domestic and foreign regulations in respect of fatigue management crew member. Also, I suggest legal proposals for amendment of Korea Aviation act and Enforcement Regulations concerning fatigue management for crew members. I hope that this paper is helpful to change korea fatigue regulations, to enhance aviation safety, and to reduce the number of accidents relating to fatigue. Fatigue should be managed at all level such as regulators, experts, operators and pilots. Authority should change surveillance mind-set from regulatory auditor to expert adviser. Operators should identify various fatigue factors and consider to crew scheduling them. Crews should strongly manage both individual and duty-oriented fatigue issues.

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