THE COMPUTING MODEL OF THE EXPERIMENTS AT PETRA III

The PETRA storage ring at DESY in Hamburg has been refurbished to become a highly brilliant synchrotron radiation source (now named PETRA III [1]). In comparison with the DORIS beamlines, the PETRA III experiments have larger complexity, higher data rates and require an integrated system for data storage and archiving, data processing and data distribution. Tango [2] and Sardana [3] are the main components of our online control system. Tango serves as the backbone to operate all beamline components, certain storage ring devices and equipment from our users. Sardana is an abstraction layer on top of Tango. It standardizes the hardware access, organizes experimental procedures, has a command line interface and provides widgets for graphical user interfaces. The high brilliance together with the rapid read-out of modern 2D detectors dramatically increase the data rates and volumes. At PETRA III all data are transfered to an online file server which is hosted by the DESY computer center. Near real time analysis and reconstruction steps are executed on a CPU farm. A portal for remote data access is in preparation. Data archiving is done by dCache [4]. An offline file server has been installed for further analysis and inhouse data storage.