With great power come great I/O issues

Despite the muscle of today's premier supercomputing systems, scaling and I/O often prevent leading software packages from taking full advantage of the latest hardware's potential power. These ancillary tasks take precious time and resources away from studying the fundamental science that impacts our everyday lives.

To address these issues, a team of researchers from Oak Ridge National Laboratory (ORNL), Georgia Tech, and Rutgers University developed the ADaptable I/O file System (ADIOS). ADIOS is an I/O middleware package that has shown great promise with leading fusion codes, scaling up to 140,000 cores for XGC-1, GTC, and GTS, and in astrophysics with the CHIMERA code. Recently, ADIOS made its mark in the field of combustion.

Researchers at Sandia National Laboratory (Ray Grout, Jackie Chen, and Chun Sang Yoo) and Andrea Gruber of SINTEF, the largest independent research organization in Scandinavia, are using the leading combustion code S3D to perform the first direct numerical simulations of reacting jets in cross flow. These transverse jets are a class of flows used in practical applications in which high mixing rates are desirable -- for example, in fuel injection nozzles in stationary gas turbines for power generation or in aero-gas turbines. The gas turbine industry is faced with numerous R&D challenges in adapting conventional hydrocarbon burner designs to operate safely and cleanly with hydrogen-rich syngas.

Though the S3D team was able to fully scale the code to ORNL's entire Cray XT5 supercomputer, known as Jaguar, the scaling of the I/O proved to be difficult. Enter ADIOS.

Besides its ability to scale, ADIOS's BP file format is resilient to failures in the compute nodes and the file system, an attribute that hinted to researchers that S3D's analysis routines would pair well with the ADIOS ecosystem. After consultations with ORNL's Qing Liu and Scott Klasky (a leading ADIOS developer) and Georgia Tech's Jay Lofstead, Chen's post-doc Ray Grout decided to integrate ADIOS as an alternative I/O mechanism for S3D. ADIOS quickly surpassed the networking limitations imposed by the previous I/O stack.

"I appreciate the clean yet capable interface and that from my perspective, it just works," said Grout. "It would have been fairly difficult for us to get this work finished in time for our targeted paper deadline using our previous I/O solution, but now I'm confident that we'll make it thanks to ADIOS and the help of its team."

S3D's newfound scalability and flexible architecture has led a member of the S3D team, ORNL's Ramanan Sankaran, to explore creating a custom I/O transport method to perform special manipulations to the I/O and the data. With this new transport method, no source code changes would be required.

Thanks to the seamless integration of ADIOS into S3D, the middleware's 1.0 release may have already achieved the team's goal of satisfying 90 percent of ADIOS users "out of the box," said Klasky, adding, "It's really exciting to be able to help the top scientists such as Ray and Jackie obtain results more efficiently. These results make a difference in the world and will hopefully make the world a better place to live."

The ADIOS team thanks all of the scientists who have helped make this work possible, including Hasan Abbasi, Julian Cummings, Divya Dinkar, Ciprian Docan, Stephane Ethier, Garth Gibson, Steven Hodson, Scott Klasky, Zhihong Lin, Qing Liu, Jay Lofstead, Xiaosong Ma, Ron Oldfield, Manish Parashar, Norbert Podhorszki, Milo Polte, Alex Romosan, Ramanan Sankaran, Karsten Schwan, Arie Shoshani, Mladen Vouk, Matthew Wolf, Yong Xiao, Weikuan Yu, and Fang Zhang.

For more information, contact Scott Klasky at klasky@ornl.gov.