• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.108-114
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• 2008

Since flash memory cannot be overwritten, new data are updated in new area. If data are frequently updated, garbage collection which is achieved by erasing blocks, should be performed to reclaim new area. Hence, because the count of erase operations is limited due to characteristics of flash memory, every block should be evenly written and erased. However, if data with access locality are processed by cost benefit algorithm with separation of hot block ad cold block though the performance of processing is hight wear-leveling is not even. In this paper, we propose CB-MB (Cost Benefit between Multi Bank) algorithm in which hot data are allocated in one bank and cold data in another bank, and in which role of hot bank and cold bank is exchanged every period. CB-MB shows that its performance is 30% better than cost benefit algorithm with separation of cold block and hot block its wear-leveling is about a third of that in standard deviation.

• The KIPS Transactions:PartD
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• v.18D no.1
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• pp.35-44
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• 2011

Memory errors can cause not only program malfunctions but also even unexpected system halt. Though a programmer checks memory errors, some memory errors with low occurrence frequency are missed to detect. In this paper, we propose a method for effectively detecting such memory errors using instruction transition diagrams through analyzing assembly codes obtained by disassembling an executable file. Out of various memory errors, local memory return errors, null pointer access errors and uninitialized pointer access errors are targeted for detection. When applying the proposed method to various programs including well-known open source programs such as Apache web server and PHP script interpreter, some potential memory errors are detected.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.938-941
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• 2010

Though a compiler checks memory errors, it is difficult for the compiler to detect function pointer errors in code level. Thus, in this paper, we propose a method for effectively detecting Invalid function pointer access errors, by analyzing assembly codes that are obtained by disassembling an executable file. To detect the errors, assembly codes in disassembled files are checked out based on the instruction transition diagrams which are constructed through analyzing normal usage patterns of function pointer access. When applying the proposed method to various programs having no compilation error, a total of about 500 potential errors including the ones of well-known open source programs such as Apache web server and PHP script interpreter are detected among 1 million lines of assembly codes corresponding to a total of about 10 thousand functions.

• The Journal of Society for e-Business Studies
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• v.9 no.1
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• pp.83-104
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• 2004

Recently, information systems that require storage and retrieval of huge amount of data are becoming used widely. Accordingly, research efforts have been made to develop Linux cluster file systems in the SAN environment in which clients themselves can manage metadata and access data directly. Also a semi-flat directory structure based on extendible hashing has been proposed to support fast retrieval of files[1]. In this research, we have designed and implemented the semi-flat extendible hash directory under the Linux system. In order to evaluate the practicality of the directory, we have also implemented the B+-tree based directory and experimented the performance. According to the performance comparisons, the extendible hash directory has the better performance at insert, delete, and search operations. On the other hand, the B+-tree directory is better at sorting files.

• Journal of Korea Multimedia Society
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• v.11 no.10
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• pp.1420-1426
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• 2008

The most recent programs tend to use picture or audio files which need mass storage resources. For these mass storages, the performance of automatic management decreases as the sizes of these resources increases. Moreover, the more the number of resources increases, the more the management of resources gets difficult. This paper suggests a resource management system to which the interface of tree-structure file system is applied in order to increase convenience and efficiency. The system uses the access technique based on character string path to have more compatibility, and supports tree structure which is more systematic. Further, it supports virtual nodes to show high performance. The system can be used to control resources from outside as well as inside of processes.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.3
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• pp.13-19
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• 2016

Spark, an in-memory big-data processing framework is popular to use for real-time processing workload. Spark can store all intermediate data in the cluster memory so that Spark can minimize I/O access. However, when the resident memory of workload is larger that the physical memory amount of the cluster, the total performance can drop dramatically. In this paper, we analyse the factors of bottleneck on PageRank Application that needs many memory through experiment, and cluster the Spark with Tachyon File System for using memory to solve the factor of bottleneck and then we improve the performance about 18%.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2002.06a
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• pp.177-184
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• 2002

In these day, the storage capacity has been growing and the informations increase in geometrically progression in a modem information age. At present the situation is required that the exchanges and access of the informations is available without regard to time and space. In this paper we present a effective backup systems to backup the information of server that continuously has to be accessible in 365's days. There are two backup cases. one is a file-base backup and the other is a block-based backup. In general, a block-based backup has a good performance than a file-based backup but it is difficult to implement a block-based systems. First, we introduce the technique of backup and methods, on-line backup. Next, we present our backup systems based on client-server model and have a snapshot facility. Finally we introduce SCSI-Protocol in order to increase the data transfer rate.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.4 no.1
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• pp.85-102
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• 1980

Accepting the necessity for maintaining the objectives of the existing circulation system, the computer-based system could be designed by the system analyst and librarians to gain a variety of improvements in the maintenance, accessibility of circulation records and more meaningful statistical records. If the terminal can be operated on-line, then this circulation data is transmitted directly to the computer, where it may update to the circulation file immediately or alternatively be kept in direct access file for updating in batch mode. on-line system in the circulation operations is "data-collection system" and "Bar-coded label system" Bar-coded label system is simple, quick, and error-free input of data. Attached to CRT terminal is a "light pen" which is hand held and will read a bar-coded label as the pen is passed over the labels (one affixed to the book itself, other carried on the borrower cards). Instantaneously the data concerning transaction is stored in the central mini-computer. It is useful, economical for us to co-operate many libraries in Korea and design borrower's ID code, book no., classification code in the Bar-coded label system by the members of the computer center and the library staff at every stage. As for book loan, the borrowers ID code, book number and classification code are scanned by the bar-code scanner or light pen and the computer decides whether to loan and store the data. The visual display unit shows the present status of a borrowers borrowing and decides whether borrower can borrow.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1204-1211
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• 2004

As the development of information telecommunication technology and thus the information sharing and opening is accelerated, f system is exposed to various threatener and the avrious security incident is rasing its head with social problem. As countermeasure, to protect safely and prepare in the attack for a system from a be latent security threat, various security systems are been using such as IDS, Firewall, VPN etc.. But, expertise or expert is required to handle security system. The module, implemented in this paper, is based on Windows XP, like Linux and Unix, and has effect integrity and non-repudiation for a file.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.763-767
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• 2005

RAID were proposed to stored double data or used to parity logging methode for error recovery. We describe a technique for automating the execution of redundant disk array operation, including recovery from errors, independent of array architecture. RAID5 provide highly reliable cost effective secondary storage with high performance for read access and large write accessed. It discusses the two architectural techniques used in disk arrays, striping across multiple disks to improve performance and redundancy to improve reliability. In this paper we compare with performance and reliability in RAID5 real/write to file and stripe size. than suggest to algorithm.