Our new system SuperMUC has been ranked as No. 4 of the world's fastest supercomputers. We will start initial user operation with selected projects on July 30, 2012 (10:00 AM). The first projects to access the system have been selected from the last Gauss Call and from those which recently consume the major part of resources on SuperMIG. These users will be contacted by LRZ individually soon. Some time later, LRZ will proceed to ramp up usage until regular user operation will be reached approximately end of August. We ask all users who gain initial access to SuperMUC to be fair by migrating their jobs to the new system as fast as possible and thereby removing their job load from SuperMIG. We expect that during early user operation we still need to flush out glitches. Therefore, early users must expect unannounced or very short-term scheduled maintenances. Early users are encouraged to report any observed problems via the LRZ service desk. Differences between SuperMIG and SuperMUC usage * Node architecture: SuperMUC is comprised of 16-way Sandy Bridge nodes; these are equipped with 32 GBytes of main memory much less than the SuperMIG nodes. Due to OS requirements, probably 26 GBytes per node will be available in user space. LRZ will also allow usage of logical hardware threads (SMT/Hyperthreads), enabling use of up to 32 tasks per node), however this resource is also partially used by OS services, and it is very much application dependent whether any performance improvement can be derived from use of SMT. * Code compatibility: It is highly recommended to rebuild separate executables for use on SuperMUC. While the compilers and basic libraries will be the same as on SuperMIG, the new architecture supports additional instructions (AVX SIMD extension), and IBM has implemented a major new version of the parallel environment (including the MPI library). Both of these may inhibit backward compatibility, and we d like to avoid having to deal with a lot of incidents reporting such (not really solvable) compatibility issues. * File systems: The file systems pointed to by the $SCRATCH and $WORK environment variables will be the new, and vastly larger and better-performing GPFS file systems. The $HOME file system will be still shared between SuperMIG and SuperMUC. We will provide additional information on how to transfer data between the non-shared SuperMIG and SuperMUC file systems via the file system documentation. Documentation The LRZ SuperMUC web page will be updated to reflect the changes discussed above. In particular the new LoadLeveler job classes and keywords and the file systemss will be documented; it may take some time before other parts of the documentation are complete. Diese Information finden Sie im WWW unter http://www.lrz-muenchen.de/services/compute/supermuc/aktuell/ali4369/ Matthias Brehm