Jun Okitsu

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X-NAS (eXpandable network attached storage), a highly scalable, distributed file system designed for entrylevel NAS, has been developed. It virtualizes multiple NAS systems into a single-file-system view for different kinds of clients. The core of X-NAS is a multi-protocol virtualized file system (MVFS), and its key features—a smart-code wrapper daemon,(More)
Gas District Cooling (GDC) plants, designed to be environmentally efficient, require frequent maintenances, in order to avoid corrosions or leakages from the chemical reactions in Steam Absorption Chillers (SACs) of the plant. However, most of the plant experts face difficulty that the positive and the negative effects from the SAC maintenances are not(More)
A priority metric for IT equipment is proposed, and a method for extracting it from historical sensor data is devised. The proposed method consists of classification of cooling efficiency from sampled sensor data and calculation of the priority metric from statistics on these cooling-efficiency classes. A proof-of-concept experiment using the priority(More)
Gas District Cooling (GDC) provides electricity and chilled water to facilities with relatively low running cost and has the potential to reduce CO2 emission as it can make effective use of wasted energy. However, the present CO2 emission tends to be higher than expected due to the chilled water supply-demand gap. To efficiently manage the gap, this paper(More)
In recent years, increasing demand for computing has led to the development of computational grid. Typically scheduling challenges tend to be NP-hard problems where there is no optimal solution. The research reported here therefore is focused on the development of hybrids scheduling algorithms based on deadline and slack time parameters and its variations,(More)
Electricity consumption for cooling purpose is known to be the most expensive operational cost factor in data centers. Inefficient cooling leads to high temperature and this in turn leads to hardware failure. This paper proposes a Thermal Aware Modified Least Slack Time Round Robin Based (MLST-RR) scheduling algorithm that can avoid high thermal stress(More)
In large gas district cooling plant, chillers' performance bottleneck analysis is important not only for anomaly detection, but also for energy optimal operations. Currently many researches adopt linear or non-linear regression correlation analysis methods to detect chiller's bottleneck, however their works majorly focus on single chiller's anomaly factors(More)
Free cooling has become widely used in the area of computer room thermal control, especially where the temperature constraint can be relaxed. However, in tropical regions, such as Malaysia, free cooling cannot be applied all of the time. This paper presents a strategy for grids that allows jobs to be executed on resources that are free cooled. The paper(More)
An on-line backup function for X-NAS, a clustered NAS system designed for entry-level NAS, has been developed. The on-line backup function can replicate file objects on XNAS to a remote NAS in real-time. It makes use of the virtualized global file system of X-NAS, and sends NFS write operations to both X-NAS and the remote backup NAS at the same time. The(More)
As one of the core cooling equipment in district cooling system, latest electric chiller can achieve high energy efficiency and low CO<sub>2</sub> emission. In recent years, many researches have been conducted on cooling plant performance evaluation and anomaly detection, but very few can quantitatively detect root causes of electric chiller's performance(More)