• 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.

• Journal of Internet Computing and Services
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• v.6 no.4
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• pp.47-58
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• 2005

There are two major type of flash memory products, namely, NAND-type and NOR-type flash memory. NOR-type flash memory is generally deployed as ROM BIOS code storage because if offers Byte I/O and fast read operation. However, NOR-type flash memory is more expensive than NAND-type flash memory in terms of the cost per byte ratio, and hence NAND type flash memory is more widely used as large data storage such as embedded Linux file systems. In this paper, we designed an efficient flash memory file system based an Embedded system and presented to make up for reduced to Swapping a weak System Performance to flash file system using NAND-type flash memory, then proposed Swapping algorithm insured to an Execution time. Based on Implementation and simulation studies, Then, We improved performance bases on NAND-type flash memory to the requirement of the embedded system.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.11
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• pp.497-508
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• 2008

Mobile Multimedia File System, MNFS, is a file system which extensively exploits NAND FLASH Memory, Since general Flash file systems does not precisely meet the criteria of mobile devices such as MP3 Player, PMP, Digital Camcorder, MNFS is designed to guarantee the optimal performance of FLASH Memory file system. Among many features MNFS provides, there are three distinguishable characteristics. MNFS guarantees, first, constant response time in sequential write requests of the file system, second, fast file system mounting time, and lastly least memory footprint. MNFS implements four schemes to provide such features, Hybrid mapping scheme to map file system metadata and user data, manipulation of user data allocation to fit allocation unit of file data into allocation unit of NAND FLASH Memory, iBAT (in core only Block Allocation Table) to minimize the metadata, and bottom-up representation of directory. Prototype implementation of MNFS was tested and measured its performance on ARM9 processor and 1Gbit NAND FLASH Memory environment. Its performance was compared with YAFFS, NAND FLASH File system, and FAT file system which use FTL. This enables to observe constant request time for sequential write request. It shows 30 times faster mounting time to YAFFS, and reduces 95% of HEAP memory consumption compared to YAFFS.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.7
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• pp.515-519
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• 2009

As the application fields of sensor nodes are getting diverse these days, it is required to have a way of collecting various data that is suitable for these application fields. In the case that the real-time surveillance over the data is unnecessary, present data collecting methods, which collect and transfer the data directly, can cause a waste of energy and data loss, A new method that store the collected data in a local storage and acquire them by query later on is required for nonreal-time applications. NAND flash has energy efficiency and large capacity so it is suitable for sensor nodes, Sensor nodes support 4-10 KBytes small sized memory and it is hard to build an effective file system since NAND Flash doesn't support overwriting NAND flash. This paper discusses an implementation of NAND Flash file system in sensor node environments. The file system makes long-term data collecting possible by reducing transmission cost. It is expected that this file system will play a central role in sensor network environments as it can be applied to various fields which call for long term data collecting.

• Journal of Information Processing Systems
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• v.2 no.3 s.4
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• pp.147-152
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• 2006

NAND flash memory-based embedded systems are becoming increasingly common. These embedded systems have to provide a fast boot time. In this paper, we have designed and proposed a flash file system for embedded systems that require fast booting. By using a Flash Image Area, which keeps the latest flash memory information such as types and status of all blocks, the file system mounting time can be reduced significantly. We have shown by experiments that our file system outperforms YAFFS and RFFS.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.651-660
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• 2008

Flash memory is widely used in embedded systems because of its benefits such as non-volatile, shock resistant, and low power consumption. However, NAND flash memory suffers from out-place-update, limited erase cycles, and page based read/write operations. To solve these problems, YAFFS and RFFS, the flash memory file systems, are proposed. However YAFFS takes long time to mount the file system, because all the files are scattered all around flash memory. Thus YAFFS needs to fully scan the flash memory. To provide fast mounting, RFFS has been proposed. It stores all the block information, the addresses of block information and meta data to use them at mounting time. However additional operations for the meta data management are decreasing the performance of the system. This paper presents a new NAND flash file system called ERFFS (Efficient and Reliable Flash File System) which provides fast mounting and recovery with minimum mata data management. Based on the experimental results, ERFFS reduces the flash mount/recovery time and the file system overhead.

• Journal of the Korea Society of Computer and Information
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• v.22 no.9
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• pp.1-8
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• 2017

In this paper, we propose a file system for flash memory which remedies shortcomings of existing flash memory file systems. Besides supporting large block size, the proposed file system reduces time in initializing file system significantly by adopting logical address comprised of erase block number and bitmap for pages in the block to find a page. The file system is suitable for embedded systems with limited main memory since it has small in-memory data structures. It also provides efficient management of obsolete blocks and free blocks, which contribute to the reduction of file update time. Finally the proposed file system can easily configure the maximum file size and file system size limits, which results in portability to emerging larger flash memories. By conducting performance evaluation studies, we show that the proposed file system can contribute to the performance improvement of embedded systems.

• The KIPS Transactions:PartA
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• v.12A no.7 s.97
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• pp.571-582
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• 2005

NAND flash memory has advantages of non-volatility, little power consumption and fast access time. However, it suffers from inability that dose not provide to update-in-place and the erase cycle is limited. Moreover, the unit of read and write operations is a page. A NAND flash file system called YAFFS has been proposed. But YAFFS has several problems to be addressed. In this paper, the Reliable Flash File System(RFFS) for NAND flash memory is designed and evaluated. In designing a file system the following four issues must be considered in particular for the design: (i) to minimize a repairing time when the system fault occurs, (ii) to balance the number of block erase operations by offering wear leveling policy, and (iii) to reduce turnaround time of memory operations by reducing the amount of data written. We demonstrate and evaluate the performance of the proposed schemes.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.251-255
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• 2008

In most file systems, if a file is deleted, only the metadata of the file is deleted or modified and the file's data is still stored on the physical media. Some users require that deleted files no longer be accessible. This requirement is more important in embedded systems that employ flash memory as a storage medium. In this paper, we propose a secure deletion method for NAND flash file system and apply the method to YAFFS. Our method uses encryption to delete files and forces all keys of a specific file to be stored in the same block. Therefore, only one erase operation is required to securely delete a file. Our simulation results show that the amortized number of block erases is smaller than the simple encryption method. Even though we apply our method only to the YAFFS, our method can be easily applied to other NAND flash file systems.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.2
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• pp.27-34
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• 2013

NAND Flash Memory has been used in several devices by low cost and high capacity, and the demand for mass NAND Flash Memory has increased due to the multimedia extension of mobile devices. The JFFS2, NILFS2, and YAFFS2 file systems are used mainly in NAND Flash Memory. In this paper, the performance of Sequential read/write of the 3 file systems are analyzed for the 4 I/O schedulers : CFQ(Complete Fair Queuing) I/O scheduler, NOOP(No Operation) I/O scheduler, Anticipatory I/O scheduler, and Deadline I/O scheduler. In JFFS2 file system, Anticipatory I/O scheduler has the best performance by 8% decreasing speed in writing time and 1.5% decreasing speed in reading time compared to the other I/O scheduler. In YAFFS2 file system, it results are similar to performance in reading and writing for the 4 I/O schedulers. In NILFS2 file system, NOOP I/O scheduler has 2% faster in writing and Deadline I/O scheduler has 6% faster in reading than other I/O schedulers.