Yahoo's Eric Baldeschwieler reports that Yahoo is now running a 10k+ core Hadoop cluster that holds over 5 petabytes of data.
Very cool. It appears Yahoo has now achieved most of the Hadoop design requirements they laid out back in July 2006.
Note, however, that 10k cores is quite a bit smaller than Google's cluster appears to be. Google used 11k machine years of computation in their cluster in Sept 2007, suggesting that they have at least 133k machines in their clusters (and likely substantially more).
Please see also my July 2006 post, "Yahoo building Google FS clone?", and my April 2007 post, "Yahoo Pig and Google Sawzall".