hadoop-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Chris Nauroth <cnaur...@hortonworks.com>
Subject Re: How to lower the total number of map tasks
Date Tue, 02 Oct 2012 17:00:26 GMT
Those numbers make sense, considering 1 map task per block.  16 GB file /
64 MB block size = ~242 map tasks.

When you doubled dfs.block.size, how did you accomplish that?  Typically,
the block size is selected at file write time, with a default value from
system configuration used if not specified.  Did you "hadoop fs -put" the
file with the new block size, or was it something else?

Thank you,
--Chris

On Tue, Oct 2, 2012 at 9:34 AM, Shing Hing Man <matmsh@yahoo.com> wrote:

>
>
>
> I am running Hadoop 1.0.3 in Pseudo  distributed mode.
> When I  submit a map/reduce job to process a file of  size about 16 GB, in
> job.xml, I have the following
>
>
> mapred.map.tasks =242
> mapred.min.split.size =0
> dfs.block.size = 67108864
>
>
> I would like to reduce   mapred.map.tasks to see if it improves
> performance.
> I have tried doubling  the size of  dfs.block.size. But
> the    mapred.map.tasks remains unchanged.
> Is there a way to reduce  mapred.map.tasks  ?
>
>
> Thanks in advance for any assistance !
> Shing
>
>

Mime
View raw message