Speaker
Federica Fanzago
(INFN-PADOVA)
Description
The CMS experiment will produce a large amount of data (few PBytes each year) that
will be distributed and stored in many computing centres spread in the countries
participating to the CMS collaboration and made available for analysis to world-wide
distributed physicists.
CMS will use a distributed architecture based on grid infrastructure to analyze data
stored at remote sites, to assure data access only to authorized users and to ensure
remote resources availability.
Data analisys in a distributed environment is a complex computing task, that assume
to know which data are available, where data are stored and how to access them.
The CMS collaboration is developing a user friendly tool, CRAB (Cms Remote Analysis
Builder), whose aim is to simplify the work of final users to create and to submit
analysis jobs into the grid environment. Its purpose is to allow generic users,
without specific knowledge of grid infrastructure, to access and analyze remote data
as easily as in a local environment, hiding the complexity of distributed
computational services.
Users have to develop their analisys code in an interactive environment and decide
which data to analyze, providing to CRAB data parameters (keywords to select data and
total number of events) and how to manage produced output (return file to UI or store
into remote storage).
CRAB creates a wrapper of the analisys executable which will be run on remote
resources, including CMS environment setup and output management. CRAB splits the
analisys into a number of jobs according to user provided information about number of
events. The job submission is done using grid workload management command.
The user executable is sent to remote resource via inputsandbox, together with the
job. Data discovery, resources availability, status monitoring and output retrieval
of submitted jobs are fully handled by CRAB.
The tool is written in python and have to be installed to the User Interface, the
user access point to the grid.
Up to now CRAB is installed in ~45 UI and about ~210 different kind of data are
available in ~40 remote sites.
The weekly rate of submitted jobs is ~10000 with a success rate about 75%, that means
jobs arrive to remote sites and produce outputs, while the remnant 25% aborts due to
site setup problem or grid services failure.
In this report we will explain how CRAB is interfaced with other CMS/grid services
and will report the daily user's experience with this tool analyzing simulated data
needed to prepare the Physics Technical Design Report.
Summary
Report about CRAB, a tool for CMS analysis in grid environment: how it is interfaced
with CMS/grid services and user's experience.
Authors
Alessandra Fanfani
(Bologna University)
Daniele Spiga
(Perugia University)
Federica Fanzago
(INFN-PADOVA)
Marco Corvo
(CERN/CNAF)
Stefano Lacaprara
(INFN Legnaro)
Co-authors
Giovanni Ciraolo
(Firenze University)
Nicola De Filippis
(Bari University)
Nikolai Smirnov
(INFN-PADOVA)
