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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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centerqi hu 2012-10-07, 13:56
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Michael Segel 2012-10-07, 14:45
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centerqi hu 2012-10-07, 15:28
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Bertrand Dechoux 2012-10-07, 19:31
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paritosh ranjan 2012-10-07, 19:49
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Harsh J 2012-10-07, 22:46
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Michael Segel 2012-10-08, 00:13
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Bertrand Dechoux 2012-10-08, 05:44
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Re: What is the difference between Rack-local map tasks and Data-local map tasks?
Definitely, If data local map tasks are more the performance will be improved much.

Ideally if data is uniformly distributed across DNs and if you have enough number of map task slots on colocated TTs then most of your map tasks should be Data Local. You may have just a few non data local map tasks when the number of input splits/map tasks are large which is quite common.

Regards
Bejoy KS

Sent from handheld, please excuse typos.

-----Original Message-----
From: centerqi hu <[EMAIL PROTECTED]>
Date: Sun, 7 Oct 2012 23:28:55
To: <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: Re: What is the difference between Rack-local map tasks and
 Data-local map tasks?

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

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pengwenwu2008 2012-12-13, 06:22