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MapReduce, mail # user - How do I diagnose a really slow copy

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How do I diagnose a really slow copy
Steve Lewis 2011-11-04, 15:20
I have been finding a that my cluster is running abnormally slowly
A typical reduce task reports
reduce > copy (113 of 431 at 0.07 MB/s)
70 kb / second is a truely dreadful rate and tasks are running much slower
under hadoop than the
same code on a the same operations on a single box -
Where do I look to find why IO operations might  be so slow??

Steven M. Lewis PhD