High-Energy Physics Applications on the Grid - Grid Computing: Infrastructure, Service, and Applications - page 440

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CERN FZK NDGF RAL TRIUMF

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FIGURE 17.9 ATLAS cosmics data acquisition (August 23-September 8, 2007). The snap-
shot of the Dashboard shows the data distribution from CERN to the main regional centers
supporting the ATLAS experiments.

EGEE project) is the i le transfer service (FTS) [23]. FTS is a layer on top of
storage (essentially SRM) and transfer protocols (globusFTP). Its main
goal is to provide a dependable service namely a layer hiding short inter-
ruptions of the underlying services (essentially by retrying) and avoiding
congestions by scheduling data transfer taking into account of the net-
work capacity and shares across users and virtual organizations.
The experiments typically contact this service to schedule a transfer and
poll it to see the status. By its nature the service collects book-keeping
information, which is also essential for the operation teams maintaining it.
In 2007, over 10 PB have been transferred. Although at this moment these
massive data movements are at the heart of the HEP applications only, I
believe that in the near future more applications will depend on it to dis-
tribute i les across vast infrastructures of storage elements.
In Figure 17.9, we show the data transfer of one of the i rst tests of the
full chain of data acquisition in late 2007. During a week, the ATLAS detec-
tor collected cosmic-ray events following the schema expected in normal
LHC operations. In this test, ATLAS distributed the raw data and the
centrally reconstructed data onto the full infrastructure (down to Tier2s).
Eventually end-users performed data analysis at the remote sites.

17.6.3 Grid Catalogs

The EGEE/LCG project has developed a very successful product called
LFC (LCG i le catalog). The LFC is a secure, lightweight, and highly scal-
able POSIX-like i le catalog serving a variety of communities. LFC stores
catalog entries on a database back-end: supported back-ends are Oracle
and MySQL.
In HEP, ATLAS uses the LFC for the local i le catalogues located at Tier0
and Tier1; these LFCs control the location of i les at each Tier1 (and related