Cloud computing helps Argonne scientists run high-energy physics experiments

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High-energy physicists at CERN in Geneva are making production runs that integrate their existing pool of distributed computers with dynamic resources in "science clouds," according to work presented at the 17th annual conference on Computing in High Energy and Nuclear Physics, held in Prague, Czech Republic, this week.

The integration was achieved by leveraging two mechanisms: the Nimbus Context Broker, developed by computer scientists at the U.S. Department of Energy's Argonne National Laboratory and the University of Chicago, and a portable software environment developed at CERN.

Scientists working on A Large Ion Collider Experiment, also known as the ALICE collaboration, are conducting heavy ion simulations at CERN. They have been developing and debugging compute jobs on a collection of internationally distributed resources, managed by a scheduler called AliEn.

Researchers sought to determine how to integrate a cloud's dynamically provisioned resources into an existing infrastructure such as the ALICE pool of computers, while still ensuring that the various AliEn services have the same deployment-specific information.

The CernVM technology was originally started with the intent of supplying portable development environments that scientists could run on their laptops and desktops. A variety of virtual image formats are now supported, including the Xen images used by the Amazon EC2 as well as Science Clouds. The challenge was to find a way to deploy these images so that they would dynamically and securely register with the AliEn scheduler and thus join the ALICE resource pool, according to Artem Harutyunyan, a graduate student at State Engineering University of Armenia and member of Yerevan Physics Institute ALICE group.

"Commercial cloud providers such as EC2 allow users to deploy groups of unconnected virtual machines, whereas scientists typically need a ready-to-use cluster whose nodes share a common configuration and security context. The Nimbus Context Broker bridges that gap," said Kate Keahey, a computer scientist at Argonne and head of the Nimbus project.

The Nimbus Context Broker enables a user to securely provide context-specific information to a virtual machine deployed on remote resources. It places minimal compatibility requirements on the cloud provider and can orchestrate information exchange across many providers.

The new system dynamically deploys a virtual machine on the Nimbus cloud at the University of Chicago, which then joins the ALICE computer pool so that jobs can be scheduled on it. Moreover, with the addition of a queue sensor that deploys and terminates virtual machines based on demand, the researchers can experiment with ways to balance the cost of the additional resources against the need for them as evidenced by jobs in a queue.