With the Large Hadron Collider starting up next year, grid sites worldwide are ramping up their equipment and service levels in preparation for an expected flood of data.

But, will they be ready—and can any problems they’re having be fixed in time?

GridPP tests its readiness

In the UK, a team from GridPP, the UK particle physics grid, has recently completed a round of visits to 17 GridPP sites, aiming to assess how ready they are for the onslaught of data that will mark the beginning of the Large Hadron Collider experiment.

Dave Britton, GridPP’s Project Manager, coordinated the process. “We wanted to check that each site would be ready for next year, and find out how we could help with any difficulties. The best way to do this was to visit each site individually, so we could talk to the people there in confidence.”

Professor Peter Hobson at Brunel University hosted one such visit, and was at initially unconvinced. “We were skeptical that this would be a useful exercise, but it was actually very helpful for us to be able to explain our priorities, constraints and concerns directly to the GridPP management.” 

Tour of duty

Since March this year, GridPP review groups have toured to each of the four Tier-2 regional centers—ScotGrid, NorthGrid, SouthGrid and London Tier 2—searching for signs of problems and challenges to come.

Tier-2s differ from their larger Tier-1 counterparts in that Tier-1s are primarily for reconstruction and long-term storage of LHC experiment data, while Tier-2s are typically used to produce simulated data and for data analysis by end users.

Dave Kelsey led the review team at ScotGrid, and found that although each site had a slightly different story, many of the same issues arose. “At all sites we were able to identify a mixture of good practice and areas where lessons could be learned from other sites,” he said.

Dave Newbold was part of the London review team: “It was good to see close links between resource providers and experimental users, which is essential for real LHC data-taking. The challenges for the future will be to keep these diverse computing resources operating in a grid environment that up to now been fairly inhomogeneous.”

The sites visits unearthed 23 issues that GridPP are now addressing, including:

• difficulties for smaller sites in meeting the two-hour response time required from Tier-2 sites;
• the complexity of installing new virtual organizations; and
• training in site monitoring using Nagios and Ganglia.

GridPP have already responded to many of the concerns raised. For example, they have developed a policy on when sites should stop stalled jobs (the first such policy for the Large Hadron Collider Computing Grid); are ensuring that security policies are harmonized so the appropriate response to any security incident is clear; and are working on issues of middleware support and release.

- Sarah Pearce, GridPP