• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.3
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• pp.491-500
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• 2013

With the advent of big data and increased costs of SSD(HDD), domestic and foreign Internet cafes and organizations have adopted NDS(No Disk System) solution recently. NDS is a storage virtualization solution based on a kind of cloud computing. It manages Operating System and applications in the central server, which were originally managed by individual computers. This research will illustrate the way to analyze user's behaviors under NDS circumstance.

• International journal of advanced smart convergence
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• v.9 no.3
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• pp.253-259
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• 2020

Most of today's large-scale cloud systems and enterprise data centers are distributing resources to improve scalability and resource utilization. NVMe-over-Fabric protocol allows submitting NVMe commands to a remote NVMe SSD through RDMA (Remote Direct Memory Access) network. It is attracting attention recently because it is possible to construct a disaggregation storage system with low latency through the protocol. However, the current I/O stack of NVMe-over-Fabric has an inefficient structure for maintaining compatibility with the traditional I/O stack. Therefore, in this paper, we propose a new mechanism to reduce I/O latency and CPU overhead by modifying I/O path of NVMe-over-Fabric to pass through legacy block layer. According to the performance evaluation results, the proposed mechanism is able to reduce the I/O latency and CPU overhead by up to 22% and 24% compared to the existing NVMe-over-Fabrics protocol, respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1145-1152
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• 2021

In order to optimize the performance of 1.4P large storage, the characteristics of each chunk mode were investigated, and the chunk 512K mode was selected in terms of I/O speed. NVME storage system was configured and used to measure data server performance of large storage. By measuring the change in throughput according to the number of threads of the 1.4P large storage, the characteristics of the large storage system were identified, and it was confirmed that the performance was up to 133Gbps with a block size of 32KB. As a result of data transmission/reception experiment using globus-url-copy of GridFTP, it was found that this large storage has a throughput of 33Gbps.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.153-165
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• 2014

Carbon dioxide capture and storage (CCS) technology is recognizing one of method responding the climate change with reduction of carbon dioxide in atmosphere. In Korea, due to its geological characteristics, sub-seabed geological $CO_2$ storage is regarded as more practical approach than on-land storage under the goal of its deployment. However, concerns on potential $CO_2$ leakage and relevant acidification issue in the marine environment can be an important subject in recently increasing sub-seabed geological $CO_2$ storage sites. In the present study effect data from literatures were collected in order to conduct an effect assessment of elevated $CO_2$ levels in marine environments using a species sensitivity distribution (SSD) various marine organisms such as microbe, crustacean, echinoderm, mollusc and fish. Results from literatures using domestic species were compared to those from foreign literatures to evaluate the reliability of the effect levels of each biological group and end-point. Ecological effect guidelines through estimating level of pH variation (${\delta}pH$) to adversely affect 5 and 50% of tested organisms, HC5 and HC50, were determined using SSD of marine organisms exposed to the $CO_2$-induced acidification. Estimated HC5 as ${\delta}pH$ of 0.137 can be used as only interim quality guideline possibly with adequate assessment factor. In the future, the current interim guideline as HC5 of ${\delta}pH$ in this study will look forward to compensate with supplement of ecotoxicological data reflecting various trophic levels and indigenous species.

• KIISE Transactions on Computing Practices
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• v.20 no.10
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• pp.525-533
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• 2014

SCST(The generic SCSI target subsystem for Linux) enables developers to make SCSI target storage and supports various SCSI network protocol such as iSCSI, FC, SRP. In this paper, we propose storage virtualization method using SCST and virtualize all flash array as high performance storage through 4Gb Fiber Channel, 10Gb Ethernet and 40Gb Infiniband and evaluate their performance, respectively. Experimental result shows that 40Gb infiniband network appliance have better performance than others. In case of sequential/random read, 40Gb infiniband network appliance shows 78% and 79% of local all flash array performance attached to SCSI target system. In case of sequential/random write, it shows 83% and 88% of local flash array performance attached to SCSI target system.

• Solar Energy
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• v.15 no.1
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• pp.13-28
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• 1995

In this study, the history of Korean traditional Ondol was investigated and the latent heat materials and bioceramics were selected to develop the latent heat storage-bioceramics Ondol system based on the Korean traditional Ondol(sensible heat storage type), and the thermal characteristics of Ondol were analyzed experimentally The results could be summarized as follows; 1. Korean traditional Ondol has been originated in "Whaduk" which had been utilized continuously for about $2{\times}10^6$ years from the Old Stone Age to the Bronze Age, and Korean traditional Ondol using in these days has been utilized for about 976 years from the Koryu Dynasty to the Modern Ages. 2. $Na_2SO_4{\cdot}10H_2O(SSD)$ was selected as latent heat material for the latent heat storage Ondol. 3. Ondol unit was filled with the latent heat material of 0.63 kg and the dimension of Ondol unit was $400mm{\times}400mm{\times}27mm(width{\t\imes}depth{\times}height)$. 4. The comfortable surface temperature($23{\sim}29^{\circ}C$) of the latent heat storage Ondol was lasted 5 hours at the room temperature of $16{\sim}18^{\circ}C$, whereas that of sensible heat storage Ondol was lasted only 1.0 hours in the same conditions. 5. For the thermal effect of bioceramics, the Ondol air temperature i.n case of bioceramics treatment on the pannel was higher than that of without bioceramics treatment.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.767-774
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• 2010

Due to advantages of NAND flash memory such as non-volatility, low access latency, low energy consumption, light weight, small size and shock resistance, it has become a better alternative over traditional magnetic disk drives, and has been widely used. Traditional DBMSs including mobile DBMSs may run on flash memory without any modification by using Flash Translation Layer (FTL), which emulates a random access block device to hide the characteristics of flash memory such as "erase-before-update". However, most existing FTLs are optimized for file systems, not for DBMSs, and traditional DBMSs are not aware of them. Also, traditional DBMSs do not consider the characteristics of flash memory. In this paper, we propose a flash-conscious storage system for DBMSs that utilizes flash memory as a main storage medium, and carefully put the characteristics of flash memory into considerations. The proposed flash-conscious storage system exploits log records to avoid costly update operations. It is shown that the proposed storage system outperforms the state.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.2
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• pp.3-13
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• 2004

DRM is the ability to brand digital contents with features that ensure copy Protection and affect the way in which digital contents are played back. DRM is a technology that enables the secure distribution, promotion and sale of digital contents on the Internet. The DRM Client System that operates on the untrusted user environments has to meet the requirements of the contents owner, including copyright and contents protection. After the DRM Client System is installed on the untrusted user environments, it verifies and plays digital contents. With these procedures it cuties out user authentication, contents decryption, and license management. During these procedures, the sensitive data, including authentication information, decryption data and license data, must be secured against any illegal access from users. The goal of this thesis is to introduce the implementation of Secure Storage Device which can protect user's authentication key, cryptographic key, and license data in safe where the DRM Client System is running.

• Journal of the Korea Society of Computer and Information
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• v.21 no.5
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• pp.1-10
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• 2016

Magnetic disks have been used for decades in auxiliary storage devices of computer systems. In recent years, the use of NAND flash memory, which is called SSD, is increased as auxiliary storage devices. However, NAND flash memory, unlike traditional magnetic disks, necessarily performs the erase operation before the write operation in order to overwrite data and this leads to degrade the system lifetime and performance of overall NAND flash memory system. Moreover, NAND flash memory has the lower endurance, compared to traditional magnetic disks. To overcome this problem, this paper proposes EPET (Enhanced Prediction and Elapsed Time) wear leveling technique, which is especially efficient to portable devices. EPET wear leveling uses the advantage of PET (Prediction of Elapsed Time) wear leveling and solves long-term system failure time problem. Moreover, EPET wear leveling further improves space efficiency. In our experiments, EPET wear leveling prolonged the first bad time up to 328.9% and prolonged the system lifetime up to 305.9%, compared to other techniques.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.291-302
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• 2013

NAND flash memory (NFM) based storage devices, e.g. Solid State Drive (SSD), are rapidly replacing conventional storage devices, e.g. Hard Disk Drive (HDD). As NAND flash memory technology advances, its specification has evolved to support denser cells and larger pages and blocks. However, efforts to fully understand their impacts on design objectives such as performance, power, and cost for various applications are often neglected. Our research shows this recent trend can adversely affect the design objectives depending on the characteristics of applications. Past works mostly focused on improving the specific design objectives of NFM based systems via various architectural solutions when the specification of NFM is given. Several other works attempted to model and characterize NFM but did not access the system-level impacts of individual parameters. To the best of our knowledge, this paper is the first work that considers the specification of NFM as the design parameters of NAND flash storage devices (NFSDs) and analyzes the characteristics of various synthesized and real traces and their interaction with design parameters. Our research shows that optimizing design parameters depends heavily on the characteristics of applications. The main contribution of this research is to understand the effects of low-level specifications of NFM, e.g. cell type, page size, and block size, on system-level metrics such as performance, cost, and power consumption in various applications with different characteristics, e.g. request length, update ratios, read-and-modify ratios. Experimental results show that the optimized page and block size can achieve up to 15 times better performance than the conventional NFM configuration in various applications. The results can be used to optimize the system-level objectives of a system with specific applications, e.g. embedded systems with NFM chips, or predict the future direction of NFM.