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From Jinyan Xu <Jinyan...@exar.com>
Subject when hadoop report job finished?
Date Wed, 15 Feb 2012 03:39:57 GMT

Hi all,

I run terasort test on pseudo distributed, I  found the one reduce job finished time is shorter
than the four reduces job. I used tool to search why.
Use nmon to monitor the disk read/write operation, I found a phenomena, when one reduce job
report finished but the disk write data operation is still sustained for a long time. For
four reduce jobs, when job report finished the disk read/write operation is done.

In a nutshell, one reduce job finished time add disk write operation time equal to four reduces
job finished time.

So I think this is the reason why one reduce job time is shorter than the four reduces job,
finally, I want to ask why that happened?  What is the reduce job finished mark?

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