<http://googleblog.blogspot.com/2008/11/sorting-1pb-with-mapreduce.html> "It took six hours and two minutes to sort 1PB (10 trillion 100-byte records) on 4,000 computers." The inevitability of using 48,000 HDDs: "every time we ran our sort, at least one of our disks managed to break" -andyf