[show abstract][hide abstract] ABSTRACT: The CERN facility hosts the Tier-0 of the four LHC experiments, but as part of WLCG it also offers a platform for production activities and user analysis. The CERN CASTOR storage technology has been extensively tested and utilized for LHC data recording and exporting to external sites according to experiments computing model. On the other hand, to accommodate Grid data processing activities and, more importantly, chaotic user analysis, it was realized that additional functionality was needed including a different throttling mechanism for file access. This paper will describe the xroot-based CERN production and analysis facility for the ATLAS experiment and in particular the experiment use case and data access scenario, the xrootd redirector setup on top of the CASTOR storage system, the commissioning of the system and real life experience for data processing and data analysis.
Journal of Physics Conference Series 12/2011; 331(7):072006.
[show abstract][hide abstract] ABSTRACT: The use of proxy caches has been extensively studied in the HEP environment for efficient access of database data and showed significant performance with only very moderate operational effort at higher grid tiers (T2, T3). In this contribution we propose to apply the same concept to the area of file access and analyse the possible performance gains, operational impact on site services and applicability to different HEP use cases. Base on a proof-of-concept studies with a modified XROOT proxy server we review the cache efficiency and overheads for access patterns of typical ROOT based analysis programs. We conclude with a discussion of the potential role of this new component at the different tiers of a distributed computing grid.
Journal of Physics Conference Series 12/2011; 331(7):072010.
[show abstract][hide abstract] ABSTRACT: The parallel ROOT facility, PROOF, enables the interactive analysis of distributed data sets in a transparent way. It exploits the inherent parallelism in data sets of uncorrelated events via a multi-tier architecture that optimizes I/O and CPU utilization in heterogeneous clusters with distributed storage. On a grid, PROOF can use the available services to find out the location of data to analyze and the resources to use. Dedicated PROOF-enabled test-beds are now being deployed for testing by the LHC experiments. Being part of the ROOT framework PROOF inherits the benefits of a high performance object-oriented storage system and a wealth of statistical and visualization tools. The basic ideas and architecture underlying the PROOF project are described, together with the status of the project, focusing mostly on the issues of data access optimization, scheduling of user sessions and user interface
Proceedings of the 15th IEEE International Symposium on High Performance Distributed Computing, HPDC-15, Paris, France, June 19-23, 2006; 01/2006
[show abstract][hide abstract] ABSTRACT: The Parallel ROOT Facility, PROOF, enables the analysis of much larger data sets on a shorter time scale. It exploits the inherent parallelism in data of uncorrelated events via a multi-tier architecture that optimizes I/O and CPU utilization in heterogeneous clusters with distributed storage. The system provides transparent and interactive access to gigabytes today. Being part of the ROOT framework PROOF inherits the benefits of a performant object storage system and a wealth of statistical and visualization tools. This paper describes the data analysis model of ROOT and the latest developments on closer integration of PROOF into that model and the ROOT user environment, e.g. support for PROOF-based browsing of trees stored remotely, and the popular TTree::Draw() interface. We also outline the ongoing developments aimed to improve the flexibility and user-friendliness of the system.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment - NUCL INSTRUM METH PHYS RES A. 01/2006; 559(1):13-16.
[show abstract][hide abstract] ABSTRACT: This paper describes an efficient method for access authorization in distributed (grid) storage systems. Client applications obtain "access tokens" from an organization's file catalogue upon execution of a file name resolution request. Whenever a client application tries to access the requested files, the token is transparently passed to the target storage system. Thus the storage service can decide on the authorization of a request without itself having to contact the authorization service. The token is protected from access and modification by external parties using public key infrastructure. A prototype using the AliEn grid file catalogue and xrootd as a data server has been implemented. A detailed description of the prototype implementation is presented.
Grid Computing, 2005. The 6th IEEE/ACM International Workshop on; 12/2005
[show abstract][hide abstract] ABSTRACT: The ARDA project aims to provide end-to-end systems for physics analysis for the LHC experiments. In collaboration with the experiments, prototype systems are being developed that are based on the experimental software and on the middleware under development within the EGEE project – gLite. The strategy of the ATLAS experiment is to develop high level services that supports physics analysis and simplifies grid usage for the physicist. A first implementation of such a service, DIAL, has already been developed and interfaces to conventional batch systems such as LSF or Condor. In this report first experiences using ATLAS software with the gLite prototype are described. The integration of ATLAS software components with the prototype is discussed. Some aspects of job execution, data management, metadata and Software installation are considered. A first implementation of a DIAL service based on the middleware prototype is demonstrated.