FAQ
Hi, according to Hadoop The Definitive Guide , map will store the
intermediate output to a in-memory buffer first, and the spill it to local
disk which configured by mapred.local.dir, so from i knew, if the
intermediate data lost , only redo can fix it.

if i wrong, please correct me.

2010/9/27 Nan Zhu <zhunansjtu@gmail.com>
Hi, all

I'm not sure which mail list I should send my question to, sorry for any
inconvenience I brought

I'm interested in that how hadoop handles the lost of intermediate data
generated by map tasks currently, as some papers suggest, for the
situation
that the data needed by reducers are lost, we should compare the cost
leading by redo the task and replicating the data, if redoing the task
costs
more, we can offer more replication of the intermediate data generated by
map to ensure that reducers can access the data, otherwise, we just redo
the
corresponding map task when we detect the lost

I'm not sure what's the strategy adopted by hadoop currently, I haven't
find
the code on this function, can anyone give me some suggestions?

Thank you

Nan

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postedSep 27, '10 at 5:36a
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