Sharing lattice QCD data over a widely distributed file system

JLDG is a data-grid for the lattice QCD (LQCD) community in Japan. Several large research groups in Japan have been working on lattice QCD simulations using supercomputers distributed over distant sites. The JLDG provides such collaborations with an efficient method of data management and sharing. File servers installed on 9 sites are connected to the NH SINET VPN and are bound into a single file system with the GFarm. The file system looks the same from any sites, so that users can do analyses on a supercomputer on a site, using data generated and stored in the JLDG at a different site. We present a brief description of hardware and software of the JLDG, including a recently developed subsystem for cooperating with the HPCI shared storage, and report performance and statistics of the JLDG. As of April 2015, 15 research groups (61 users) store their daily research data of 4.7PB including replica and 68 million files in total. Number of publications for works which used the JLDG is 98. The large number of publications and recent rapid increase of disk usage convince us that the JLDG has grown up into a useful infrastructure for LQCD community in Japan.