We propose an information-sharing network system, capable of forming and dynamically reconfiguring multiple information-sharing groups on the same network platform by using wavelength routing and distributed shared memory technologies. The network system comprises information-sharing terminal nodes equipped with a shared memory and a wavelength-tunable transmitter, network management terminal and an arrayed-waveguide grating (AWG). The information-sharing terminal nodes are connected to an AWG by a pair of optical fibers, forming a star-shaped topology. Information is shared among the information-sharing terminal nodes through the establishment of a logical information-sharing ring. This is accomplished by adjusting the output of the wavelength-tunable transmitter at each terminal node to an appropriate wavelength according to the wavelength-routing characteristics of the AWG wavelength router. We developed a prototype information-sharing network system, in which, as preliminary experiments, HDTV and SDTV videos were used for real-time information sharing. The dynamic reconfiguration of information-sharing groups and a simple automatic restoration technique have been successfully demonstrated. The system is applicable to distributed computer processing systems and high-capacity information-sharing applications such as high-quality videoconferences.

In this paper, we propose a workload assignment policy for reducing power consumption by air conditioners in data centers. In the proposed policy, to reduce the air conditioner power consumption by raising the temperature set points of the air conditioners, the temperatures of all server back-planes are equalized by moving workload from the servers with the highest temperatures to the servers with the lowest temperatures. To evaluate the proposed policy, we use a computational fluid dynamics simulator for obtaining airflow and air temperature in data centers, and an air conditioner model based on experimental results from actual data center. Through evaluation, we show that the air conditioners' power consumption is reduced by 10.4% in a conventional data center. In addition, in a tandem data center proposed in our research group, the air conditioners' power consumption is reduced by 53%, and the total power consumption of the whole data center is exhibited to be reduced by 23% by reusing the exhaust heat from the servers.