Applying Pwrake Workflow System and Gfarm File System to Telescope Data Processing

In this paper, we describe a use case applying a scientific workflow system and a distributed file system to improve the performance of telescope data processing. The application is pipeline processing of data generated by Hyper Suprime-Cam (HSC) which is a focal plane camera mounted on the Subaru telescope. In this paper, we focus on the scalability of parallel I/O and core utilization. The IBM Spectrum Scale (GPFS) used for actual operation has a limit on scalability due to the configuration using storage servers. Therefore, we introduce the Gfarm file system which uses the storage of the worker node for parallel I/O performance. To improve core utilization, we introduce the Pwrake workflow system instead of the parallel processing framework developed for the HSC pipeline. Descriptions of task dependencies are necessary to further improve core utilization by overlapping different types of tasks. We discuss the usefulness of the workflow description language with the function of scripting language for defining complex task dependency. In the experiment, the performance of the pipeline is evaluated using a quarter of the observation data per night (input files: 80 GB, output files: 1.2 TB). Measurements on strong scaling from 48 to 576 cores show that the processing with Gfarm file system is more scalable than that with GPFS. Measurement using 576 cores shows that our method improves the processing speed of the pipeline by 2.2 times compared with the method used in actual operation.