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Hadoop, mail # user - io.sort.factor


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Ajay Srivastava 2013-01-23, 06:23
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bharath vissapragada 2013-01-23, 06:44
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Re: io.sort.factor
Ajay Srivastava 2013-01-23, 07:16
Hi Bharat,

I am looking at these logs -
2013-01-22 07:35:42,923 INFO org.apache.hadoop.mapred.MapTask: Finished spill 2

The number at the end of string does not go beyond 6. So I assume you are correct.
Regards,
Ajay Srivastava
On 23-Jan-2013, at 12:14 PM, bharath vissapragada wrote:

Hi,

>From my understanding, increasing "io.sort.mb" decreases the number of disk flushes as more data is spilled at once and this boosts the performance. This obviously decreases the number of spills.

One possibility in this case is that, the number of spills have become less than "io.sort.factor" and all the spills are getting merged in a single go (per partition). So even if you increase the "io.sort.factor" value now, it shouldn't make any difference. So check the logs and see the no. of spills created and if its less than "io.sort.factor".

This is a wild guess, please feel free to correct me if I'm wrong.

Thanks

On Wed, Jan 23, 2013 at 11:53 AM, Ajay Srivastava <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:
Hi,

io.sort.factor  --  The number of streams to merge at once while sorting files. This determines the number of open file handles.
How can I use this parameter to improve performance of mapreduce job?
My understanding from above description was If there are many spill records then increasing io.sort.mb as well as io.sort.factor will help in better performance. Increasing io.sort.mb helped but changing io.sort.factor (> 10) does not seem to improve/degrade performance of mapred  job.

Regards,
Ajay Srivastava