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linux.conf.au Linux: for all things great and small
linux.conf.au Linux: for all things great and small | Linux: for all things great and small |
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| Open Sauce - Linux Blog | |
| by Sam Varghese | |
| Tuesday, 18 November 2008 | |
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Page 3 of 6 Unlike many other fields where people duck responsibility, Bannon welcomes it. "We need to feel ownership of the system. You have to have people who feel that it's their baby," he says. Featured Whitepaper
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Samuel agrees. "High-performance computing by its nature is a specialised area. It's not something where we can really say, we're going to put the latest update from Red Hat Linux or the latest service pack from SUSE Linux and then the user can get at it. There is a lot more tuning necessary. We do track the mainline kernel at least on the new Barcelona cluster because the new kernels do so much better on that hardware than the kernels that vendors ship. It also means that we can fix the things that vendors omit because they are not really relevant to their own customers. That gives us a lot more freedom and a lot more responsibility but it is very rewarding for us as well. And that's a big driver, i think, within the group that looks after the clusters." VPAC's latest cluster is quite a beast. "The latest machine has 760 processor cores, using quad-core Barcelona chips and 4 gig of memory per processor core. That means 32-gig per node and local scratch space of just over a terabyte," says Samuel. "We thought that was a crazy amount of disk space and then we had a test case and a user came along and said he needs 6000 gigs of scratch space to run his job and that was the only space we could run it. "It's more than just the Linux as well - we have Linux running as the kernel, all the GNU utilities that are part of the userspace and all the other bits and pieces that come as part of a distro. But on top of that there is other open source software as well. We've got things like OpenMPI. The message passing interface standard is an open one anyway and it is a way of writing explicitly parallel programs. Those stacks are important and compilers are also very important. We also have proprietary compilers from the Intel group, the Portland group, IBM compilers on our IBM cluster and we also track the GCC versions. We build things so that our users can select their combination of utilities." VPAC's clients are mostly from the scientific community. "A small proportion of our work is commercial work and within that group too probably most of them are scientists depending on how you use the term," says Bannon. "Physicists, computational chemists modelling chemical reactions, life scientists working out the molecular structures, working out how a molecule actually physically looks and then how it reacts to, for example, heat. We have lots of people running galactic simulations, looking at how galaxies form and progress and disappear, we have lots of engineering people doing computational fluid dynamics code where they might model how a flame front moves through a room in the event of a fire. For example, by working out how quickly the flame front moves through the room, you might be able to work out escape strategies." There are about 600 users, a large number, and at any one time there may be about 100 active projects and a couple of hundred active users. Samuel says they often see cycles of usage from people where they would do simulations, then go to validate and then write them up. After that there would some more work. "So people's usage tends to come and go." |
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