Information technologists refer to the GRID when talking about on-demand computing. The Internet is the worldwide system of networks that connects many computers and smaller networks, allowing them all to communicate. The Web is a way of accessing information over the Internet. The GRID is a way of using the Internet to share and manage computing resources that are distributed around the globe.
The Large Hadron Collider (LHC) holds four experiments: Alice, LHCb, CMS and ATLAS. At present, the High Energy Physics Laboratory at UAM supports the community of scientists in ATLAS.
The ATLAS experiment of the LHC (CERN) at nominal operation can produce several hundreds of Megabytes per second after all filtering stages. These data is distributed to the participating computer centers along the globe for processing and being analyzed with very time-consuming programs. These programs include Monte Carlo simulation of events according to the theoretical knowledge of nature. The amount of data accumulated per year, which needs to be stored and processed, is order 10 Petabytes (10 billions of Megabytes). This unprecedented amount of data to be processed by complex time-consuming analysis programs and thousands of users located all around the Globe, led to the construction of a distributed GRID infrastructure able to store and process the data in parallel.
The Worldwide LHC Computing Grid ( WLCG ) is the computing framework that implements such distributed infrastructure, built on the ideas of grid technology initially proposed in 1999 by Ian Foster and Carl Kesselman ( GRID-2 ). The WLCG is composed of four levels, or “Tiers”, called 0, 1, 2 and 3. Each Tier is made up of several computer centres and provides a specific set of services. Tier 0 is the CERN Data Centre. Tier-1 stores data and perform large-scale reprocessing. Tier-2 handle a proportional share of the production and reconstruction of simulated events.
Since 2002 the High Energy Physics Laboratory at UAM operates a Grid center in the context of the WLCG. The center supports simulation and end-user processing of the data, thus, placing us as a Tier-2 since the begining of the LHC operation in 2008.
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