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MapReduce >> mail # user >> max 1 mapper per node


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Re: max 1 mapper per node
For terasort you want to fill up your entire cluster with maps/reduces as fast as you can to get the best performance.

Just play with #slots.

Arun

On May 9, 2012, at 12:36 PM, Jeffrey Buell wrote:

> Not to speak for Radim, but what I’m trying to achieve is performance at least as good as 0.20 for all cases.  That is, no regressions.  For something as simple as terasort, I don’t think that is possible without being able to specify the max number of mappers/reducers per node.  As it is, I see slowdowns as much as 2X.  Hopefully I’m wrong and somebody will straighten me out.  But if I’m not, adding such a feature won’t lead to bad behavior of any kind since the default could be set to unlimited and thus have no effect whatsoever.
>  
> I should emphasize that I support the goal of greater automation since Hadoop has way too many parameters and is so hard to tune.  Just not at the expense of performance regressions.
>  
> Jeff
>  
>  
> We've been against these 'features' since it leads to very bad behaviour across the cluster with multiple apps/users etc.
>  
> What is your use-case i.e. what are you trying to achieve with this?
>  
> thanks,
> Arun
>  
> On May 3, 2012, at 5:59 AM, Radim Kolar wrote:
>
>
> if plugin system for AM is overkill, something simpler can be made like:
>
> maximum number of mappers per node
> maximum number of reducers per node
>
> maximum percentage of non data local tasks
> maximum percentage of rack local tasks
>
> and set this in job properties.
>  
>  

--
Arun C. Murthy
Hortonworks Inc.
http://hortonworks.com/
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB