About map and reduce maximum concurrency number settings

Source: Internet
Author: User
Keywords concurrency Value name can reboot
About map and reduce the maximum number of concurrent Settings blog Category: Test hadoop&http://www.aliyun.com/zixun/aggregation/37954.html ">nbsp;

I. Environmental

1. Hadoop 0.20.2

2, operating system Linux

Ii. Setting up

1, because Hadoop cluster all machines can not be completely configured, so the different node machines concurrent maximum map and reduce number of the best not the same.

2, modify the Mapreduce-sit.xml file on the corresponding node machine, add the following parameters:

<property> <name>mapred.tasktracker.map.tasks.maximum</name> <value>2</value> <description>the Maximum number of map tasks that'll be run simultaneously by a task tracker. </description></property><property> <name>mapred.tasktracker.reduce.tasks.maximum</ name> <value>2</value> <description>the Maximum number of reduce tasks that'll be run Simultaneously by a task tracker. </description></property>

This field value can be different on each node machine.

3, view the http://192.168.3.131:50030/machines.jsp?type=active to check the number.

Iii. Summary

1, after configuration, do not need to restart the cluster of all the machines, just restart your modified node machine can be.

2, if the Web page can not see the change, then execute any job, the value will highlight the change.

3, combined with the fair scheduler to use, can maximize performance.

From: http://blog.csdn.net/dajuezhao/article/details/5809788

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