09.03.10
by

Ben Segal, LHC@home starts to tackle real LHC physics

LHC accelerates protons and particles, analysis of resulting events is helping understand the nature of matter, origin of the universe etc.

LHC@home is based on BOINC, to allow volunteers to lend their computers, started five years ago. Was a tool to help design and tune the accelerator itself. Beams circulate and collide many times per second. Objectives were to raise awareness of CERN and the LHC, as well as providing extra CPU power.

Project has run intermittently, which the volunteers don’t really like. Hoping to start giving them a steady flow of jobs in the next few months.

Now want to do “real physics”.

Serious challenges:

  • Most volunteers run Windows, but experiments run on Linux and exporting to Windows is impractical. Didn’t have that problem with design project.
  • Code canges often, so all PCs must update
  • Code size very big

Solution:

Can we use virtualisation? Entire applications environment is packaged, sent out as a ‘virtual image’ and executed in a virtual machine.

Result:

Coding proting to Windows happens automatically. But the problem is the virtual image is still very big (10 Gbtes), and must rewrite whole virtual image for each update.

So there’s a solution but it’s not very practical.

CernVM – when mainframes ruled the roost, IBM mainframe was called CernVM. It was replaced by PCs and Unix/Linux.

The new CernVM is a ‘thin’ virtual appliance for the LHC experiments. Racks of virtual machines. Provides a complete, portable and easy way to configure user env for running locally, on a grid or in the cloud.

New LHC@Home project will use CernVM. Sends user 0.1 GB, it logs into system and downloads rest up to 1GB, and never has to load the full 10GB. Can run real physics with just 1GB.

However, that’s not the end of it. System runs on BOINC, which needs the jobs to be sent from the physicists. But they won’t change their current set up to produce BOINC jobs – they want to know where their jobs are and be able to manage them, and BOINC doesn’t allow that. Their job submission system does do that.

CernVM has software image control, also added an interface for job management.

All done by students and volunteers, which makes it a bit intermittent.