Dr Peter Elmer (Princeton University (US))
Deploying the Worldwide LHC Computing Grid (WLCG) was greatly facilitated by the convergence, around the year 2000, on Linux and commodity x86 processors as a standard scientific computing platform. This homogeneity enabled a relatively simple "build once, run anywhere" model for applications. A number of factors are now driving interest in alternative platforms. Power limitations at the level of individual processors, and in aggregate in computer centers, place greater emphasis on power efficiency issues. The rise of mobile computing, based primarily on ARM processors with a different intellectual property model, has also created interest in ARM as an potential general purpose architecture for the server market. We report our experience building a demonstrator Grid cluster using systems with ARMv8 64-bit processors, capable of running production-style workflows. We present what we have learned regarding the use of both application and Open Science Grid (OSG) software on ARMv8 64-bit processors, as well as issues related to the need to manage heterogeneous mixes of x86_64 and ARMv8 64-bit processors in a Grid environment. We also report the hardware experience we have gained while building the cluster.