• Title, Summary, Keyword: Clustered Hash Table

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A Clustered Flash Translation Layer for Mobile Storage Systems (휴대용 저장장치 시스템을 위한 Clustered Flash Translation Layer)

  • Park, Kwang-Hee;Kim, Deok-Hwan
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.45 no.3
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    • pp.94-100
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    • 2008
  • It is necessary to develop the flash memory system software FTL(Flash Translation Layer) which is used in mobile storage like Compact Flash memory. In this paper, we design the FTL using clustered hash table and two phase software caching method to translate logical address into physical address fastly. The experimental results show that the address translation performance of CFTL is 13.3% higher than that of NFTL and 8% higher than that of AFTL, and the memory usage of CFTL is 75% smaller than that of AFTL.

Anticipatory I/O Management for Clustered Flash Translation Layer in NAND Flash Memory

  • Park, Kwang-Hee;Yang, Jun-Sik;Chang, Joon-Hyuk;Kim, Deok-Hwan
    • ETRI Journal
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    • v.30 no.6
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    • pp.790-798
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    • 2008
  • Recently, NAND flash memory has emerged as a next generation storage device because it has several advantages, such as low power consumption, shock resistance, and so on. However, it is necessary to use a flash translation layer (FTL) to intermediate between NAND flash memory and conventional file systems because of the unique hardware characteristics of flash memory. This paper proposes a new clustered FTL (CFTL) that uses clustered hash tables and a two-level software cache technique. The CFTL can anticipate consecutive addresses from the host because the clustered hash table uses the locality of reference in a large address space. It also adaptively switches logical addresses to physical addresses in the flash memory by using block mapping, page mapping, and a two-level software cache technique. Furthermore, anticipatory I/O management using continuity counters and a prefetch scheme enables fast address translation. Experimental results show that the proposed address translation mechanism for CFTL provides better performance in address translation and memory space usage than the well-known NAND FTL (NFTL) and adaptive FTL (AFTL).

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Clustered Segment Index Scheme for P2P VOD Service on Virtual Mesh Overlay Network (가상 메시 오버레이 네트워크상에서의 P2P VOD 서비스를 위한 클러스터 세그먼트 인덱스 기법)

  • Lim, Pheng-Un;Choi, Hwang-Kyu
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.6
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    • pp.1052-1059
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    • 2016
  • Video-on-Demand(VoD) is one of the most popular media streaming which attracted many researchers' attention. VMesh is one of the most cited works in the field of the VoD system. VMesh is proposed to solve the problem of random seeking functionality. However, a large number of the DHT(Distributed Hash Table) searches in VMesh is sill the main problem which needs to be solved. In order to reduce the number of the DHT searches, the clustered segment index(CSI) scheme is proposed. In this scheme, the video segments are divided into clusters. The segment information of the video segments, which are clustered into the same cluster, are stored in the same clustered segment index that can be searched by using the hash key. Each peer also can request the required segments by using this clustered segment index. The experiment results show that the number of the DHT searches in the proposed scheme is less than that of VMesh even in case of peers leave and join the network or peers perform the fast forward/backward operations.

Efficient Prefetching and Asynchronous Writing for Flash Memory (플래시 메모리를 위한 효율적인 선반입과 비동기 쓰기 기법)

  • Park, Kwang-Hee;Kim, Deok-Hwan
    • Journal of KIISE:Computing Practices and Letters
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    • v.15 no.2
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    • pp.77-88
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    • 2009
  • According to the size of NAND flash memory as the storage system of mobile device becomes large, the performance of address translation and life cycle management in FTL (Flash Translation Layer) to interact with file system becomes very important. In this paper, we propose the continuity counters, which represent the number of continuous physical blocks whose logical addresses are consecutive, to reduce the number of address translation. Furthermore we propose the prefetching method which preloads frequently accessed pages into main memory to enhance I/O performance of flash memory. Besides, we use the 2-bit write prediction and asynchronous writing method to predict addresses repeatedly referenced from host and prevent from writing overhead. The experiments show that the proposed method improves the I/O performance and extends the life cycle of flash memory. As a result, proposed CFTL (Clustered Flash Translation Layer)'s performance of address translation is faster 20% than conventional FTLs. Furthermore, CFTL is reduced about 50% writing time than that of conventional FTLs.

Erase Group Flash Translation Layer for Multi Block Erase of Fusion Flash Memory (퓨전 플래시 메모리의 다중 블록 삭제를 위한 Erase Croup Flash Translation Layer)

  • Lee, Dong-Hwan;Cho, Won-Hee;Kim, Deok-Hwan
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.46 no.4
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    • pp.21-30
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    • 2009
  • Fusion flash memory such as OneNAND$^{TM}$ is popular as a ubiquitous storage device for embedded systems because it has advantages of NAND and NOR flash memory that it can support large capacity, fast read/write performance and XIP(eXecute-In-Place). Besides, OneNAND$^{TM}$ provides not only advantages of hybrid structure but also multi-block erase function that improves slow erase performance by erasing the multiple blocks simultaneously. But traditional NAND Flash Translation Layer may not fully support it because the garbage collection of traditional FTL only considers a few block as victim block and erases them. In this paper, we propose an Erase Group Flash Translation Layer for improving multi-block erase function. EGFTL uses a superblock scheme for enhancing garbage collection performance and invalid block management to erase multiple blocks simultaneously. Also, it uses clustered hash table to improve the address translation performance of the superblock scheme. The experimental results show that the garbage collection performance of EGFTL is 30% higher than those of traditional FTLs, and the address translation performance of EGFTL is 5% higher than that of Superblock scheme.