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MapReduce >> mail # user >> What is the difference between Rack-local map tasks and Data-local map tasks?


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Re: What is the difference between Rack-local map tasks and Data-local map tasks?
One thing to look for would be the block size and input split size. In case
the input split size is greater than block size, then the task might pick
blocks which are not on the same node. So, keeping the input split size
less than or equal to block size might help.

HTH,
Paritosh

On Mon, Oct 8, 2012 at 1:01 AM, Bertrand Dechoux <[EMAIL PROTECTED]> wrote:

> Basically, more replicas.
>
> The second solution would be to use a 'smarter' scheduler. In theory, the
> jobtracker should be able to say "postpone this task until a data-local
> task can be created". But I don't think any stable and public available
> scheduler do that at the moment. This would allow you to have less traffic
> but the whole job might be slower due to the wait. It might be a good trade
> if you have multiple jobs running at the same time and if your hot data is
> uniformly distributed. But in practice this is of course not always the
> case and you also need to consider sla for the users so the whole is not
> trivial.
>
> Regards
>
> Bertrand
>
>
> On Sun, Oct 7, 2012 at 5:28 PM, centerqi hu <[EMAIL PROTECTED]> wrote:
>
>> Very good explanation,
>> If there is a way to reduce Rack-local map tasks
>> but can increase the Data-local map tasks ,
>> Whether to increase performance?
>>
>> 2012/10/7 Michael Segel <[EMAIL PROTECTED]>
>>
>>> Rack local means that while the data isn't local to the node running the
>>> task, it is still on the same rack.
>>> (Its meaningless unless you've set up rack awareness because all of the
>>> machines are on the default rack. )
>>>
>>> Data local means that the task is running local to the machine that
>>> contains the actual data.
>>>
>>> HTH
>>>
>>> -Mike
>>>
>>> On Oct 7, 2012, at 8:56 AM, centerqi hu <[EMAIL PROTECTED]> wrote:
>>>
>>>
>>> hi all
>>>
>>> When I run "hadoop job -status xxx",Output the following some list.
>>>
>>> Rack-local map tasks=124
>>> Data-local map tasks=6
>>>
>>> What is the difference between Rack-local map tasks and Data-local map
>>> tasks?
>>> --
>>> [EMAIL PROTECTED]|Sam
>>>
>>>
>>>
>>
>>
>> --
>> [EMAIL PROTECTED]|齐忠
>>
>
>
>
> --
> Bertrand Dechoux
>
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