• The Journal of the Korea Contents Association
• /
• v.15 no.4
• /
• pp.9-16
• /
• 2015

On modern operating systems such as Linux, virtual memory is a general way to provide a large address space to applications by using main memory and storage devices. Recently, storage devices have been improved in terms of latency and bandwidth, and it is expected that applications with large memory show high-performance if next-generation storage devices are considered. However, due to the overhead of virtual memory subsystem, the paging system can not exploit the performance of next-generation storage devices. In this study, we propose several optimization techniques to extend memory with next-generation storage devices. The techniques are to allocate block addresses of storage devices for write-back operations as well as to configure the system parameters, and we implement the techniques on Linux 3.14.3. Our evaluation through using multiple benchmarks shows that our system has 3 times (/24%) better performance on average than the baseline system in the micro(/macro)-benchmark.

• Journal of KIISE
• /
• v.43 no.8
• /
• pp.841-847
• /
• 2016

As network technology advances, a larger number of devices are connected through the Internet. Recently, cloud storage services are gaining popularity, as they are convenient to access anytime and anywhere. Among cloud storage services, object storage is the representative one due to their characteristics of low cost, high availability, and high durability. One limitation of object storage services is that they can access data on the cloud only through the HTTP-based RESTful APIs. In our work, we resolve this limitation with the in-memory file system which provides a POSIX interface to the file system users and communicates with cloud object storages with RESTful APIs. In particular, our flush mechanism is compatible with existing file systems, as it is based on the swap mechanism of the Linux kernel. Our in-memory file system backed by cloud storage reduces the performance overheads and shows a better performance than S3QL by 57% in write operations. It also shows a comparable performance to tmpfs in read operations.

• Journal of the Korean Solar Energy Society
• /
• v.27 no.1
• /
• pp.47-54
• /
• 2007

Interests on renewable energy are increased due to oil price and environmental problems aroused from the fossil energy usage. In this study, performances of a solar assisted hybrid heat pump system are analyzed by experimental method. The developed system could runs at two types of operating mode. When the storage temperature is higher than the set temperature, the stored hot water in storage tank is supplied to the load directly. On the other hand, when the storage temperature lower than the set temperature, the water inside of the storage tank is used as heat source of the heat pump. In this study, the system control temperature for the alternation of the operating mode is set to $40^{\circ}C$ of the storage tank outlet. As results, it is founded that the COP of the developed heat pump system shows between 3.0 and 3.5. It is resonable performance for the heating system with a renewable energy as secondary heat source. The solar collect used in this study could supplies heat to the storage tank at over 400 W/m2 solar intensity. If the irradiation is lower than the 400 W/m2, the circulation pump stored and it could not supply heat to the storage tank. It is found that the difference temperature between the outlet of the storage tank and collector is $3^{\circ}C$. Even though, the extended study should be conducted to get a optimum performance of the developed system with various operating condition and control strategies.

• The Journal of Fisheries Business Administration
• /
• v.30 no.1
• /
• pp.119-147
• /
• 1999

This article is subject to the rationalization of the cold-storage warehouse management, which gives the stabilization of the fishery production and the food life with respect to fisheries industry. In this point of view, the article examines to the structure of the cold-storage warehouse industry from the perspective of the industrial organization. To put it concretely, the article intends to apprehend the state of the structure of the industry and analyze the cold-storage warehouse's management activities. In addition, I try to find know the factors that affect the management performance(profitablity) of the industry through the cross-sectional correlation analysis. Finally, the conclusion of the article can be described as follows : \circled1 On the basis of the cold-storage capacity, there is the tendency that the industry concentrate in the area of Pusan(41.7%). \circled2 By formulating step of development of the industry, it is divided by six types. Type I is designed as raw material-storage warehouse for self-processing. Type IIis the raw material-storage warehouse for self-processing and storage-sale warehouse. Type III is the raw material-storage warehouse for self.distribution. Type IV is the raw material-storage warehouse for self-distribution and storage-sale warehouse. Type V is the net storage-sale warehouse. Type Ⅵ is the physical distribution center warehouse. Although each region has one representative type,6 types exist in all regions. \circled3 The competition structure of the industry has double structure on the basis of cold-storage capacity. \circled4 With respect to the management activity of the cold-storage warehouse, there is no change or even a decrease not increasing or not any change in sales from 1996 to 1997 \circled5 In order to try to induce the amount of shipper's materials, services that a cold-storage warehouse supply with its users include a custody-fee discount, a distribution-process service, a finance service, quality management service and so on. One of the best attractive services is the custody-fee service. \circled6 In the structure and management activity of the industry, the factors that affect management performance (profitablity) are a custody-fee discount, sales ability and capital structure of individual firm. Positive factor is sales ability and capital structure of individual firm. But, The custody-fee discount turns out to be a negative capital structure of individual film.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 1999.05a
• /
• pp.193-196
• /
• 1999

This paper describes one dimensional transient modeling of encapsulated ice storage tank and its experimental validation. This model simulates the performance of tile tank for charge and discharge process with brine mass flow operating conditions.

• Journal of Energy Engineering
• /
• v.15 no.3 s.47
• /
• pp.194-201
• /
• 2006

Greenhouses should be heated during nights and cold days in order to fit growth conditions in greenhouses. Ground source heat pump (GSHP) systems are recognized to be outstanding heating and cooling systems. A horizontal GSHP system with thermal storage tank was installed in greenhouse and investigated the performance characteristics. The reasons for using thermal storage tank were discussed in detail. Thermal storage tank can provide heat for heating load that is larger than GSHP system heating capacity. The results of study showed that the heating coefficient of performance of the heat pump system was 2.69.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.12
• /
• pp.1199-1203
• /
• 2010

Data transfer between host system and storage device is based on the data unit called sector, which can be varied depending on computer systems. If NAND flash memory is used as a storage device, the variant sector size can affect storage system performance since its operation is much related to sector size and page size. In this paper, we propose an efficient FTL mapping management scheme to support multiple sector size within one NAND flash memory based storage device, and analyze the performance effect and management overhead. According to the proposed scheme, the management overhead of proposed FTL management is lower than conventional scheme when various sector sizes are configured in computer systems, while performance is less degraded in comparison with single sector size support system.

• Journal of Korea Multimedia Society
• /
• v.2 no.1
• /
• pp.9-21
• /
• 1999

This paper presents the time-segmented storage structure in order to increment search performance and the two data migration strategies: migration by Time Granularity and migration by LST-GET. In the migration strategy by Time Granularity, we describe how to assign entity version to the past, current segment, and future segments. We also describe searching and moving processes for data validity at a granularity level. In the migration strategy by LST-GET, we describe how to computer the value of dividing criterion. We simulate the search performance of the proposed segmented storage structure in comparison with the conventional storage structure in comparison with the conventional storage structure in relational database system. Finally, extensive simulation studies are performed in order to compare the search performance of the migration strategies with the time-segmented storage structure.

• International Journal of Contents
• /
• v.10 no.1
• /
• pp.62-67
• /
• 2014

Usually, cloud storage systems are developed based on DFS (Distributed File System) for scalability and reliability reasons. DFSs are designed to improve throughput than IO response time, and therefore, they are appropriate for batch processing jobs. Recently, cloud storage systems have been used for update intensive applications such as OLTP and so on. However, in DFSs, in-place update operations are not carefully considered. Therefore, when updates are frequent, I/O performance of DFSs are degraded significantly. DFSs with RAID techniques have been proposed to improve their performance and reliability. Their performance degradation caused by frequent update operations can be more significant. In this paper, we propose an in-place update method for DFS RAID exploiting a differential logging technique. The proposed method reduces the I/O costs, network traffic and XOR operation costs for RAID. We demonstrate the efficiency of our proposed in-place update method through various experiments.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.7
• /
• pp.1-5
• /
• 2012

At the present time when the limits of the magnetic storage systems appear, the holographic data storage (HDS) devices with high data transfer rate and high recording density are emerging as attractive candidates for next-generation optical storage devices. In this paper, to effectively improve the detection performance that is degraded by the two-dimensional inter-symbol interference under the HDS channel environment and the pixel misalignment, an iterative two-dimensional equalization scheme is proposed based on the contraction mapping theorem. In order to evaluate the performance of the proposed scheme, for various holographic channel environments we measure the BER performance using computer simulation and compare the proposed one with the conventional threshold detection scheme, which verifies the superiority of the proposed scheme.