High-Energy Physics Applications on the Grid - Grid Computing: Infrastructure, Service, and Applications - page 427

role in providing the bulk of the computing power for simulation activities.
Smaller facilities (Tier3) do exist, essentially to perform analysis on distilled
data samples (“downloaded” from LCG centers), but are outside the scope of
the LCG project and are not discussed here.
The data rates and sizes for the i rst two years of LHC running are
summarized in Table 17.1. The luminosity is L = 2 ¥ 10 33 cm −2 s −1 in 2008
and 2009 and then it will reach L = 10 34 cm −2 s −1 in 2010 (event rate scales
up with luminosity; event sizes can also grow due to interaction pile-up).
The canonical beam time for proton-proton operations is assumed to be
10 7 seconds in 2008 and 2009. For heavy-ion running a beam time of 10 6
seconds is assumed to be L = 5 ¥ 10 26 cm −2 s −1 .
The column RAW corresponds to the so-called raw data, the events that
have been read from the experiment readout channels, assemble and pass
through a series of online i lters. These data are recorded (also on tape for
long-term custodial storage) at CERN and at Tier1 (normally guaranteeing
at least two complete copies across the whole LCG). Raw data enter in a
chain of processing steps, generating reconstructed information and anal-
ysis objects (ESD and AOD) to allow different types of physics and detec-
tor studies. The MC (MonteCarlo) columns correspond to the required
simulation data. Before the LHC starts this is the dominating activity on
the grid (both for the simulation and the corresponding analysis). The LCG
infrastructure is built out of a collaborative effort on top of other projects
and organizations like EGEE, OSG, and NDGF. All these projects have a
multiscience character, particularly prominent in the case of EGEE. In all
cases the HEP community is one of the major drivers.

TABLE 17.1
Event Rate and Data Sizes at LHC Start Up for the LHC Experiments

Rate
[Hz]

RAW
[MB]

ESD
[MB]

AOD
[kB]

MC
[MB/evt]

MC
% of real

ALICE HI 100 12.5 2.5 250 300 100

ALICE pp 100 1 0.04 4 0.4 100

ATLAS 200 1.6 0.5 100 2 20

CMS 150 1.5 0.25 50 2 100

LHCb 2000 0.025 0.025 — 0.5 20

Note: ALICE HI refers to the heavy-ion operations. All other entries correspond to the
proton-proton operations. The requirements in terms of CPU [CPU power is mea-
sured in SPECint2000, a benchmark suite maintained by the Standard Performance
Evaluation Corporation (SPEC: http://www.spec.org) to measure and compare
compute-intensive integer performances. This quantity has been found to scale well
with typical HEP applications. As an indication, a single-core Intel Pentium 4 processor
can deliver about 1700 SPECint2000. MSI2K stands for 10 6 SPECINT2000], disk and
mass storage system (MSS) are given in Table 17.2 .

Source : LCG Technical Design Report.