• The Journal of the Korea Contents Association
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• v.12 no.2
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• pp.30-39
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• 2012

In these day, some of IT venders already were going to cloud computing market, as well they are going to expand their territory for the cloud computing market through that based on their hardware and software technology, making collaboration between hardware and software vender. Distributed file system is very mainly technology for the cloud computing that must be protect performance and safety for high levels service requests as well data store. This paper introduced distributed file system for cloud computing and how to use this theory such as memory database, Hadoop file system, high availability database system. now In the market, this paper define a very large distributed processing architect as a reference by kind of distributed file systems through using technology in cloud computing market.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.1
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• pp.20-27
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• 2004

We propose the character recognition system for Gerber files. The Gerber file is the vector-formatted drawing file for PCB manufacturing, which includes various symbols, figures and characters. Also, the characters are written in horizontal, vertical, and reverse-vortical directions. In this paper, we newly propose the Gerber-character recognition system to recognize all of component names located in PCB. To improve the performance, we develop the multiple recognizers by neural networks and the verifier considering the structural features. The developed system has been installed to the auto-programming software for PCB assembly and inspection machines.

• Journal of KIISE
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• v.44 no.4
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• pp.363-373
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• 2017

Ext4 file system is widely used in various computing environments such as those of the PC, the server, and the Linux-based embedded system. Ext4, which uses a buffer for block I/O, provides fsync() system call to applications to guarantee the consistency of a specific file. A log of the analytical studies regarding the operation of Ext4 and the improvement of its performance has been compiled, but it has not been studied in detail in terms of kernel versions. We figure out that the behavior of fsync() system call is different depending on the kernel version. Between the kernel versions of 3.4.0 and 4.7.2, 3.4.0, 3.8.0, and 4.6.2 showed behavioral differences regarding the fsync() system call. The latency of fsync() in kernel 3.4.0 is longer than that of the more-advanced 3.7.10; meanwhile, the characteristics of 3.8.0 enabled the disruption of the Ext4 journaling order, but the ordered defect was solved with 4.6.2.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.4
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• pp.259-273
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• 2009

Most of large-scale distributed file systems decouple a metadata operation from read and write operations for a file. In the distributed file systems, a certain server named a metadata server (MDS) maintains metadata information in file system such as access information for a file, the position of a file in the repository, the namespace of the file system, and so on. But, the existing systems used restrictive metadata management schemes, because most of the distributed file systems designed to focus on the distributed management and the input/output performance of data rather than the metadata. Therefore, in the existing systems, the metadata throughput and expandability of the metadata server are limited. In this paper, we propose a new non-shared metadata management scheme in order to provide the high metadata throughput and scalability for a cluster of MDSs. First, we derive a dictionary partitioning scheme as a new metadata distribution technique. Then, we present a load balancing technique based on the distribution technique. It is shown through various experiments that our scheme outperforms existing metadata management schemes in terms of scalability and load balancing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.849-856
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• 2008

As the XML is used as the standard format for information delivery and exchange in various fields, the SVG is frequently used as a user interface or expression tool for the embedded system like an internet based mobile phone. The SVG file must contain additional information specifying the structure of the document and it consumes more transmission time than the actual data sent. The SMETA(Svg transmission MEthod using Semantic meTAdata) system[9] is a study to reduce the size of the SVG file by partitioning the SVG file to a minimal size and assigning meaningful meta data to each portion of the data. In this paper, instead of the meta data exchange method for reducing the size of the file exchanged in the existing SMETA system, we studied an improved version of SMETA system that analyzes the data for each user in the server system and only transmits the data that a user needs. In addition, through our simulation, we verified that it provides better performance than the existing system even if encryption is used.

• 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 Computing Science and Engineering
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• v.6 no.4
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• pp.280-286
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• 2012

The last decades have witnessed an increasingly indispensible role of high performance computing (HPC) in science, business and financial sectors, as well as military and national security areas. To introduce key aspects of HPC to a broader community, an HPC session was organized for the first time ever for the United States and Korea Conference (UKC) during 2012. This paper summarizes four invited talks that each covers scientific HPC applications, large-scale parallel file systems, administration/maintenance of supercomputers, and green technology towards building power efficient supercomputers of the next generation.

• Journal of the Korea Society of Computer and Information
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• v.15 no.5
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• pp.49-56
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• 2010

In this paper, we implement a Hadoop based cluster for cloud computing and evaluate the performance of this cluster based on application characteristics by executing RandomTextWriter, WordCount, and PI applications. A RandomTextWriter creates given amount of random words and stores them in the HDFS(Hadoop Distributed File System). A WordCount reads an input file and determines the frequency of a given word per block unit. PI application induces PI value using the Monte Carlo law. During simulation, we investigate the effect of data block size and the number of replications on the execution time of applications. Through simulation, we have confirmed that the execution time of RandomTextWriter was proportional to the number of replications. However, the execution time of WordCount and PI were not affected by the number of replications. Moreover, the execution time of WordCount was optimum when the block size was 64~256MB. Therefore, these results show that the performance of cloud computing system can be enhanced by using a scheduling scheme that considers application's characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.65-72
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• 2007

This paper aims to provide information to generate a statistical load model of an educational server by analyzing workload of an e-Learning sewer at Dankook University. The result of the analysis shows file size distribution, access frequency and transmission volume for each file type, access interval, changes in preference and clients access rate by networks. In particular, it had different results from previous studies about video file's size distribution and file distribution based on access frequency. This is because the characteristics of e-learning are influenced by using authoring tools for making into video file and by freeing the number of students who register for a course. The result in this paper can be used as a basic data for studies designed to improve e-learning system architecture and server performance.

• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.668-678
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• 2007

The development of a wire and wireless communication technologies might permit easily accessing on various information. But, the easiness of accessing information has basically the problem of an unintended information outflow. An executable file which has key algorithms, data and resources for itself has very weak point in the security. Because the various information such as algorithms, data and resources is included in an executable file on embedded systems or virtual machines, the information outflow problem may appear more seriously. In this paper, we propose a technique which can be protecting the executable file contents for resolving the outflow problem through the encryption. Experimentally, we applied the proposed technique to EVM-the virtual machine for embedded system and verified it. Also, we tried a benchmark test for the proposed technique and obtained reasonable performance overhead.