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From Brock Noland <br...@cloudera.com>
Subject Re: random seeks during write in HDFS
Date Sat, 17 Mar 2012 14:50:08 GMT

This question is for hdfs-user not mapreduce-user, as such I have removed them.

Yes HDFS does not allow ramdom writes. I suggest your read this doc:

Specifically the "Assumptions and Goals" section.

Here are two ways to get around this design assumption:

1) Write updated copies of the record with a new time stamp and then
dedup based on a unique key and timestamp.
2) Use HBase


On Sat, Mar 17, 2012 at 9:09 AM, Hassen Riahi <hassen.riahi@cern.ch> wrote:
> Hi,
> We are trying to execute a mapper making a random access during writing
> files. It seems that HDFS supports only random seek during read and not
> during write (neither the file modification). Is it right? we are using
> hadoop-0.20. If it is the case, is there any plan to support it in the
> future?
> The limitation described above makes the mapper failing to write files. Is
> there any suggestions to bypass this limitation? such as write files in a
> temp area and copying them then to HDFS?
> Thanks for the help,
> Hassen

Apache MRUnit - Unit testing MapReduce - http://incubator.apache.org/mrunit/

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