[MAPREDUCE-1333] Parallel running tasks on one single node may slow down the performance

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 0.20.1
• Component/s: jobtracker, task, tasktracker
• Assignee: Unassigned
• Reporter: Zhaoning Zhang
• Created: 25/Dec/09 03:15
• Updated: 29/Jul/14 21:40
• Resolved: 29/Jul/14 21:40

Description

When I analysis running tasks performance, I found that parallel running tasks on one single node will not be better performance than the serialized ones.
We can set mapred.tasktracker.

{map|reduce}

.tasks.maximum = 1 individually, but there will be parallel map AND reduce tasks.

And I wonder it's true in the real commercial clusters?