Group LABCOM

H. "Nakanishi

H." Sugisaki

M. Emoto

M. Kojima

M. Ohsuna

S. Komada

National Institute for Fusion Science (NIFS-Repository)

§22. Object-oriented Data Operation and Storage of the LHD Mass Data Acquisition System Nakanishi, H., Kojima, M., Ohsuna, M., Komada, S., Emoto, M. and LABCOM Group, Sugisaki, H. (CTCS) The LHD data acquisition and management system for plasma diagnostics[ 1,2], which is named as LABCOM system, has been designed to process rv 1 GB plasma raw data by the typical discharge experiment of about 10 second short-pulse duration in the continuous 3-minute cyclic operation. In order to satisfy the necessary conditions to complete to acquire and process whole diagnostic data within 100 seconds after every discharge end, it was obliged to utilize the massively paral-lel processing (MPP) structure and reduce the data processing load of the individual element, such as data 1/0 ports or cpus. After about a year LHD experiment, the total amount of the raw data from kinds of the plasma diagnostics goes up to about 250 MB per each shot, than 20 rv 30 MB in the start-up exper-imental period. CAMAC Data Acquisition on Windows NT The primary purpose of the data acquisition part of the LABCOM system is the plasma measurements of th~ physical analysis which generally requires as fast data sampling as to follow the plasma intrinsic frequencies of its dynamic behav-iors. They manages the CAMAC digitizers and transfer, trans-form and store the experimental data, where all of the process-ing sequences are executed in the pre- and post-experimental periods as they were pre-programmed. These procedure flow of the data management are often recognized as so-called the batch processing. Sub-components of the LAB COM data acquisition can be classified into the categories as listed below, 1. digitizing by CAMAC modules 2. SCSI data transfer with optical extender 3. PClWindows NT data acquisition server computers 4. data cross-referencing by virtual shared memory 5. object-oriented database on every server computer 6. harddisk array and media-changeable mass-storage As for the digitizer modules for LHD, we have to inherit a lot of CAMAC properties which had been working in the prior experimental devices of our institute. In order to manipulate the SCSI-connected CAMAC crate controller from Windows NT and to acquire the data from their modules, we have newly developed the CAMAC handling software[3]. The block data transfer between the CAMAC governing service program and the client application will be executed efficiently through the double buffering mecha-nism. The total throughput of the block data transfer is about 700kB/s between the CAMAC module and the application program. Hierarchical Data Storage The LAB COM system has applied the hierarchical storage management (HSM) technology. It had installed the 2 levels of the storage hierarchy in 1998: One is the local RAID of 50 GB for each server computer for 30 kinds of diagnostics, and the other is the 3 MO jukebox whose total volume goes up to 3.6TB. The 50 GB RAID is occupied by the database vol-ume file of the object-oriented database management system (ODBMS), and the plasma data are directly store into the database volume as the data object. The typical data stor-ing rate into the ODBMS is max. 400 kB/s, and to improve the effective rate and reduce the storage volume size, the data compression mechanism of GNU-zlib library is used toward those binary mass objects. Owing to the data compression and multi-thread programming, almost all of the server PCs can finish their acquisition and storage within 40 seconds after ev-ery experiment end. The compression rates, however, tightly depend on the signal forms; some integrated signal or pulse-count measurements achieve fine rates about a few %, while some fluctuation signals never go under 50 %. Operational Results The LABCOM system has been successfully developed with both of the strong capability of the mass data acquisition and the expansion flexibility by applying the MPP structure based on PC and Windows NT. At the end of the 2nd experi-mental term, the total amount of the plasma raw data acquired by the LAB COM system was about 120 MB/shot, excepting some kinds of the standalone acquisition systems. In the fol-lowing 1 or 2 years, it will easily reach the initial estimate of rv 1 GB/shot. Table 1: Operational achievement of the LAB COM system in the 1st and 2nd LHD experimental terms. Ist:#l rv#1888, 2nd:# 1889rv#7132. 1st term 1MB 2nd term 1MB Halpha 4,231 41,674 Bolometer 8,276 51,114 Fast Ion Gauge 1,825 7,273 Impurity Monitor 2,169 21,568 Magnetics 12,847 90,300 Langmuir Probe 6,706 58,050 mm-wave Interfero. 4,361 ECHPower 3,380 Reflectmetry 23,587 Soft-X fluc. 25,314 X-ray PHA 9,420 ICH Power 15,577 Bremsstrahlung 28,162 Fast Ion 6,860 TOTAL 43,795 378,899 References [1] Nakanishi H. et ai., 1. Plasma Fusion Res. 72 (1996) 1362. [2] Nakanishi H. et ai., Fusion Eng. Design 43 (1999) 293. [3] Kojima M. et ai., Fusion Eng. Design 43 (1999) 433. 161 

Object-oriented Data Operation and Storage of the LHD Mass Data Acquisition System

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