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Hi Rob, On 9 March 2012 16:28, Rob Fay <[log in to unmask]> wrote: > Hi Alessandra, > > On 09/03/2012 16:13, Alessandra Forti wrote: > >> Hi Rob, >>> >>> >>> This is what Manchester is doing following the Glue schema. Of course >> we loose >> out when the cluster is half full but we try to keep it full and we use >> all the >> 24 slots so not being full is less systematic than what you want to do. >> > > That's an option, but I don't think we'd really want to do that on our > nodes. Aside from the increased contention for I/O, our benchmarking shows > total HS06 not only virtually flatlines but actually goes down as you reach > full hyperthreaded capacity on these boxes - the total HS06 for 24 runs is > less than the total HS06 for 18 runs. > Sure, but if you mean you're actually benchmarking with HS06, there's a caveat to consider: real life performance of jobs (especially analysis jobs, which are more I/O, and less CPU, heavy) is not precisely HS06-like. The real-life performance figures I've managed to get out of ATLAS's experimental monitoring system (built out of HammerCloud) suggest that performance for QMUL's hyperthreaded cores converges on 50% (from above) those of non-hyperthreaded cores, for their analysis load. This is somewhat better than the pessimistic figure that HS06 gives you (although I suspect production will look more like the HS06 figures). Sam > > Cheers, > > Rob > > > -- > Robert Fay [log in to unmask] > System Administrator office: 220 > High Energy Physics Division tel (int): 43396 > Oliver Lodge Laboratory tel (ext): +44 (0)151 794 3396 > University of Liverpool http://www.liv.ac.uk/physics/** > hep/ <http://www.liv.ac.uk/physics/hep/> >