MDSplus remote data access over high latency connections

Remote data access is a mandatory requirement for large devices operated by international teams. Data acquired during experimental sessions should be soon available at remote sites for on-line analysis and visualization. Network channel capacity plays an important role, but overall performance depends also on the strategies adopted by the data system in order to optimize data transfer, increasing throughput and reducing latency. The ITER Remote Experimentation Centre (REC) in Rokkasho is one of the projects currently implemented within the Broader Approach agreement. The ultimate objective of the REC is to allow researchers to take part in the experimentation on ITER from a remote location. The technologies developed for the REC include Remote Data Access (RDA) tools, which allows the users to access to the experimental data, regardless of their geographical location. MDSplus is the most widespread data system that is used in the fusion community for remote data access and is the candidate technology for exporting ITER data at the REC. This paper reports the measured performance in remote data access between Europe and Japan using MDSplus and describes several strategies that have been adopted in order to optimize data transfer. The solutions recently implemented within MDSplus for data streaming and remote access of very large signals are also discussed, as they represent important features needed for RDA in large experiments