Page last updated at 22:51 GMT, Friday, 20 November 2009
Guide to the Large Hadron Collider



LCG computer grid farm

The Cern facility has been intimately involved in the development of computing and the internet. BBC science and technology reporter Jonathan Fildes explains why.

In 1989, a computer scientist sat at his desk in a laboratory on the French-Swiss border and changed the world.

He invented a computer system to allow jobbing physicists working on a newly built particle accelerator to easily swap data amongst themselves.

The system quickly morphed, exploding into what is known as the world wide web.

Now a team at the Cern laboratory is at it again. This time, however, rather than just allowing scientists to share information, they have built a system that will also allow them to share computer power.

It is called the Large Hadron Collider Computing Grid (LCG) and promises to transform any old desktop PC into the equivalent of a supercomputer. It has been developed to analyse the colossal amounts of data flowing from Cern's newest particle accelerator.

"When the accelerator is running, we anticipate gathering 15 petabytes of data every year," said Ian Bird, project leader at the labs.

That is enough information to fill a typical PC's hard drive every four minutes and represents just the collected data.

It is estimated that 99% of the results from the machine will be discarded almost immediately after a cursory check to make sure that they do not include anything of interest.

But even this 1% represents a torrent of data, which researchers at the facility estimate will need at least 100,000 computers to analyse.

"Our problem is that there is no way we can do all of this computing at Cern," said Mr Bird.

Two LHC Magnets
Just 1% of the data collected by the experiments will enter the grid

Global proof

Technically it was possible, he explained, but because the LHC is an international collaboration, resources and infrastructure had to be distributed around the world.

"Ultimately, the simplest technical thing to do would be find a huge, cheap piece of land, build a cheap building and put all of the computing in it - that is exactly what the likes of Google have done.

"But that wasn't feasible physically, economically or politically."

Instead they turned to grid computing.

"The Grid allows different groups to work together, to share their data, to share the computing resources, to share the results, to advance the science as quickly as possible," explained Bob Jones, a computer scientist at Cern who coordinates the European Enabling Grids for E-science (EGEE) project.

A grid is essentially a piece of software that unites tens of thousands of PCs scattered around the globe.

"From the user's point of view - he can be sitting in Oxford, Rio or anywhere; and he can execute an application on this virtual computer," said Mr Jones. "He doesn't need to know in the end where his program is going to run."

The concept was pioneered by American scientists in the early 1990s and various projects now exist around the world both for academia and business. However, many believe it will really come into its own when Cern fires up the LHC.

"When the LHC comes on stream it will be proof on a large scale that grids work," said Mr Jones.

The LCG will be the largest grid computing network in the world. It currently consists of 250 computing centres in 45 countries linked by a series of high-speed private fibre optic networks and portions of the public internet.

Cern's PC Farm
Analysing the LHC data requires far more computers than Cern can install

Web impact

"It's basically a series of layers," explained Mr Bird. "You have the network layer, which is really the cabling and the routers which provide the physical layer.

"On top of that you have the grid infrastructure which is really the mechanisms and procedures by which all the computer centres are made to look as one.

"And then on top of that you have the LCG which makes use of the underlying infrastructures but is very specific to LHC computing."

The entire network will be used by 7,000 scientists who will pore over the LHC data looking for evidence of physics' missing links, such as the elusive Higgs boson particle.

If found it would be a huge coup for science and the ultimate validation of the LHC and the grid.

Yet even without such a result, the developers of the LCG believe grid computing is already having an impact in science and in the wider world.

"Companies are selling things which perhaps they don't call grid - perhaps they talk about on demand or cloud computing - but these are technologies that have been forced through and developed for grid computing," said Mr Jones.

And its effect on science has been even more profound.

Projects are using grid technologies to screen millions of compounds for potential drugs and to comb through the vast swathes of data collected by Nasa's armada of telescopes and spacecraft, for example.

"Science is now able to do things that it has never been able to do before," said Mr Bird.

But only time will tell whether the technology will have the same impact as Cern's last and best known contribution to computing.

"I wouldn't have said the web would have had a global impact if I'd been asked in 1992," said Mr Bird. "So I refuse to predict that."



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