Dear users of the SuperMUC Petaflop system, due to a scheduled maintenance of the thin node system, no access and no user operation will be possible starting April 22, 8:00 am. The maintenance is expected to last three days. You will be updated on the status of the system via this document. After the maintenance, an updated operating environment (SLES11SP2) will be available. This information is also available on our web server http://www.lrz-muenchen.de/services/compute/supermuc/aktuell/ali4557/ Reinhold Bader