H. "Okumura

J. Kariya

M. Emoto

S." Yamaguchi

T.K. Ohska

Y. Teramati

National Institute for Fusion Science (NIFS-Repository)

§35. Scalable Real-Time Data Acquisition/ Analysis System with Multicasting Okumura, H. (Matsusaka Univ.) Kariya, J. (Yamaguchi Univ.) Teramati, Y. (Univ. lndust. Tech.) Ohska, T.K. (KEK) Emoto, M. (Nihon Sun) Yamaguchi, S. We incorporated the following three new features into our UNIX-based data acquisi-tion/ analysis system: (1) Real-time graphical monitoring. (2) Reduced network traffic using multicast-ing. (3) Character-based remote monitoring. Our system is "scalable" in that the system performance is proportional to the number of workstations conprising the system. A simple client-server system, with O(n) data-acquisition servers and 0 ( n) display/ analysis clients, is not fully scalable, because the network traffic can grow as O(n2). We used multicasting, a comparatively new mode of network communications where any number of interested workstations can listen to the same packet. In this case, the packet num-ber grows as O(n) rather than O(n2). Multicas-ting is different from conventional broadcasting, where all broadcast packets must be processed by the network drivers of all the workstations, thus degrading the performance. In the NIFS IV -coil experiment we ran our software on a very limited system comprising two workstations communicating with multicas-ting. We used Sun SPARCstations running a multicast-enabled version of Sun OS 4.1.x. One workstation, connected to a multichannel ADC (analog-to-digital converter),· sent data packets to another workstation by multicasti'ng. The lat-ter then displayed data graphically on its win-, dows. One window displayed data for several minutes, while another for several hours, an-other for several days, thus enabling easy glance of data in multiple time scales. 40 Moreover, to serve the needs of remote character-based terminals, a "guest" account was set up in one workstation, where newest thermometer readings were displayed. One point that must be borne in mind is that multicast (or broadcast) packets do not correct errors by retransmission, because many work-stations would tend to ask for retransmission of bad packets at the same time, leading to network storms. We are now developing a new packet en-coding scheme capable of error correction with-out retransmission. =!f-------1~-E ~~-----+------~--1 ~ ~ ~-~ ~L:~----~U:~<l:-47~~-~~:~~:47---Fig. 1. Real-time monitoring system. References 1) Kariya, J. et al. 51st Meeting on Cryogen-ics and Superconductivity, Book of Abstracts (1994), 227. 1) Yamaguchi, S. et al. 51st Meeting on Cryo-genics and Superconductivity, Book of Ab-stracts (1994), 226. 1) Yamaguchi, S. et al. 52nd Meeting on Cryo-genics and Superconductivity, Book of Ab-stracts ( 1994), 264. 1) Kariya, J. et al. 52nd Meeting on Cryogen-ics and Superconductivity, Book of Abstracts (1994), 265. 2) Okumura, H. et al. To be published in Pro-ceedings of 18th SOFT. 

Scalable Real-Time Data Acquisition/ Analysis System with Multicasting

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