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From Devaraj k <devara...@huawei.com>
Subject RE: Map slots and Reduce slots
Date Mon, 15 Jul 2013 01:57:00 GMT
Hi Shekar,

   I assume you are trying with Hadoop-1. There are no properties with the names 'mapred.map.max.tasks'
and 'mapred.reduce.max.tasks'.

We have these configuration to control the max no of map/reduce tasks run simultaneously.
mapred.tasktracker.map.tasks.maximum - The maximum number of map tasks that will be run simultaneously
by a task tracker.
mapred.tasktracker.reduce.tasks.maximum - The maximum number of reduce tasks that will be
run simultaneously by a task tracker.

For ex: If we declare mapred.tasktracker.map.tasks.maximum=3  and mapred.tasktracker.reduce.tasks.maximum=4
for a task tracker, means the TT has 3 map slots and 4 reduce slots.

> Let's say on a machine if i have 8GB RAM and dual core machine, how can i determine that
what would be the optimal number of map and reducer slots for this machine
It purely depends on which type of tasks you are going to run and load of the task. Normally
each task requires one core to execute, no of concurrent tasks can be configured based on
this. And memory required for the task depends on how much data it is going to process.


Thanks
Devaraj k

From: Shekhar Sharma [mailto:shekhar2581@gmail.com]
Sent: 14 July 2013 23:15
To: user@hadoop.apache.org
Subject: Map slots and Reduce slots

Does the properties mapred.map.max.tasks=3 and mapred.reduce.max.tasks=4 means that machine
has 3 map slots and 4 reduce slots?

Or is there any way i can determine the number of map slots and reduce slots that i can allocate
for a machine?

Let's say on a machine if i have 8GB RAM and dual core machine, how can i determine that what
would be the optimal number of map and reducer slots for this machine




Regards,
Som Shekhar Sharma
+91-8197243810

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