• The Magazine of the IEIE
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• v.37 no.3
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• pp.61-70
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• 2010

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.55-57
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• 2005

최근 들어 PDA, 스마트카드, 휴대폰, MP3 플레이어 등과 같은 이동 컴퓨팅 장치의 데이터 저장소로 플래시 메모리를 많이 사용하고 있다. 이런 이동 컴퓨팅 장치의 데이터를 효율적으로 삽입$\cdot$삭제$\cdot$검색하기 위한 색인기법이 필요하다. 기존연구에서는 BFTL(B-Tree Flash Translation Layer)기법을 사용하여 플래시 메모리 상에 B-트리 구축 시 쓰기연산을 감소시켜 비용을 줄였지만, B-트리 검색비용과 하드웨어 구성비용이 증가한다는 단점을 가지고 있다. 본 논문에서는 기존 연구의 문제점을 개선하고 효율적으로 플래시 메모리상에 B-트리를 구현하기위해 BOF(B-Tree On Flash Memory)기법을 제안한다. 이 기법을 통해 BFTL 기법에 근접하는 구축비용을 얻을 수 있을 뿐만 아니라 상당한 검색비용을 줄일 수 있다. 또한 하드웨어적 비용도 고려하여 저비용으로 B-트리를 구현하였다.

• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.109-114
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• 2024

Enterprise storage systems that require high data reliability are applying RAID (Redundant Array of Independent Disks) systems to recover from data loss and failure. In particular, RAID 5 ensures space efficiency and reliability by distributing parity across multiple storage devices. However, when storage devices have different capacities, RAID is built based on the smallest capacity storage device, resulting in wasted storage space. Therefore, research is needed to solve this resource management problem. In this paper, we propose a method for RAID grouping of each independent NAND flash memory block in a RAID consisting of SSD (Solid State Disk) with external SSDs as well as internal SSDs. This method is divided into a policy for delivering block information inside SSDs to the RAID system and a policy for RAID grouping of physical addresses delivered from the RAID system. This method allows us to maintain a RAID that does not waste resources when SSDs of different capacities are grouped into RAID5. Finally, we demonstrate the effectiveness of the proposed method through experiments.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1035-1038
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• 2008

가상 메모리의 스왑 저장 장치로서 플래시 메모리를 사용하는 경우, 시스템을 기동할 때 스왑 영역의 초기화를 위한 삭제 연산이 요구되어 기동 시간이 오래 걸리는 문제점이 있다. 본 논문에서는 스왑 영역의 플래시 메모리 내용을 모두 삭제하지 않고 일부만을 삭제함으로서 기동 시간을 줄일 수 있는 방법을 연구하였다.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.8
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• pp.758-762
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• 2008

Embedded systems usually utilize Flash Memories with very nice characteristics of non-volatility, low access time, low power and so on. For the multimedia database systems, R-tree is an indexing tree with nice characteristics for multimedia access. MR-tree, which is an upgraded version of R-tree, has shown better performance in searching, inserting and deleting operations than R-tree. Flash memory has sectors and blocks as a unit of read, write and delete operations. Especially, the delete is done on a unit of 512 byte blocks with very large operation time and it is also known that read and write operations on a unit of block matches caching nature of MT-tree. Our research optimizes MR-tree operations in a unit of Flash memory blocks. Such an adjusting leads in better indexing performance in database accesses. With MR-tree on a 512B block units we achieved fast search time of database indexing with low height of MR-tree as well as faster update time of database indexing with the best fit of flash memory blocks. Thus MR-tree with optimized operations shows good characteristics to be a database index schemes on any systems with flash memory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.436-439
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• 2011

As mobile digital devices have come into more widespread use, the demand for mobile storage devices have been increasing rapidly and most of digital cameras and camcorders are using SD memory cards. The SD memory card are generally employing a form of copying data into a personal computer after storing user data based on flash memory. The current paper proposes the SD memory card of being capable of storing photograph and image data through network rather than using a method of storing data in flash memory. By delivering data and memory address values obtained through SD Slave IP to network server without sending them to flash memory, one can store data necessary to be stored in a computer's SD memory in real time in a safe and convenient way.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.189-191
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• 2007

본 논문은 하이브리드 저장 장치를 위한 효율적인 병렬 저장 시스템 구조와 데이터 및 파일 관리 기술 개발을 목표로 한다. 기존의 플래시 메모리 기반의 기존의 데이터 저장 구조들을 분석하고, 병렬형 하이브리드 데이터 저장 시스템 구조와 비교 분석한다. 또한, 하이브리드 하드 디스크의 데이터 저장 및 입출력 연산 수행을 효과적으로 지원할 수 있도록 플래시 메모리의 고유한 특성을 활용한 상황 인지 데이터 및 파일 관리 기법을 제안한다.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.383-384
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• 2007

본 논문은 하이브리드 저장 장치를 위한 효율적인 병렬 저장 시스템 구조와 데이터 및 파일 관리 기술 개발을 목표로 한다. 기존의 플래시 메모리 기반의 기존의 데이터 저장 구조들을 분석하고, 병렬형 하이브리드 데이터 저장 시스템 구조와 비교 분석한다. 또한, 하이브리드 하드디스크의 데이터 저장 및 입출력 연산 수행을 효과적으로 지원할 수 있도록 플래시 메모리의 고유한 특성을 활용한 상황인지 데이터 및 파일 관리 기법을 제안한다.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.12
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• pp.683-695
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• 2007

NAND flash memory-based file systems cannot store their system-related information in the file system due to wear-leveling of NAND flash memory. This forces NAND flash memory-based file systems to scan the whole flash memory during their mounts. The mount time usually increases linearly according to the size of and the usage pattern of the flash memory. NAND flash memory has been widely used as the storage medium of mobile devices. Due to the fact that mobile devices have unstable power supply, the file system for NAND flash memory requires stable recovery mechanism from power failure. In this paper, we present design and implementation of a new NAND flash memory-based file system that provides fast mount and enhanced stability. Our file system mounts 19 times faster than JFFS2's and 2 times faster than YAFFS's. The stability of our file system is also shown to be equivalent to that of JFFS2.

• The KIPS Transactions:PartD
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• v.18D no.3
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• pp.157-168
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• 2011

Recently flash memory has been being utilized as a main storage device in mobile devices, and flashSSDs are getting popularity as a major storage device in laptop and desktop computers, and even in enterprise-level server machines. Unlike HDDs, on flash memory, the overwrite operation is not able to be performed unless it is preceded by the erase operation to the same block. To address this, FTL(Flash memory Translation Layer) is employed on flash memory. Even though the modified data block is overwritten to the same logical address, FTL writes the updated data block to the different physical address from the previous one, mapping the logical address to the new physical address. This enables flash memory to avoid the high block-erase cost. A flashSSD has an array of NAND flash memory packages so it can access one or more flash memory packages in parallel at once. To take advantage of the internal parallelism of flashSSDs, it is beneficial for DBMSs to request I/O operations on sequential logical addresses. However, the B-tree structure, which is a representative index scheme of current relational DBMSs, produces excessive I/O operations in random order when its node structures are updated. Therefore, the original b-tree is not favorable to SSD. In this paper, we propose AS(Always Sequential) B-tree that writes the updated node contiguously to the previously written node in the logical address for every update operation. In the experiments, AS B-tree enhanced 21% of B-tree's insertion performance.