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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-72) hadoop doesn't take advatage of distributed compiting in TestDFSIO
Date Thu, 09 Mar 2006 20:40:43 GMT
hadoop doesn't take advatage of distributed compiting in TestDFSIO
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         Key: HADOOP-72
         URL: http://issues.apache.org/jira/browse/HADOOP-72
     Project: Hadoop
        Type: Test
  Components: dfs, fs, mapred  
 Environment: 200 node cluster
    Reporter: Konstantin Shvachko


TestDFSIO runs N map jobs, each either writing to or reading from a separate file of the same
size, 
and collects statistical information on its performance. 
The reducer further calculates the overall statistics for all maps. 
It outputs the following data:
- read or write test
- date and time the test finished   
- number of files
- total number of bytes processed
- overall throughput in mb/sec
- average IO rate in mb/sec per file

__Results__
I run 7 iterations of the test one after another on a cluster of ~200 nodes. 
The file size is the same in all cases 320Mb. 
The number of files tried is 1,2,4,8,16,32,64.
The log file with statistics is attached.
It looks like we don't have any distributed computing here at all.
The total execution time increases proportionally to the total size of data both for writes
and reads.
Another thing is that the io ratio for read is higher than the write rate just gradually.
For comparison I attach time measuring for the same ios performed on the same cluster but
sequentially in a simple loop.
This is the summary:

Files	map/red time	sequential time
 1		49			  34 
 2		86			  69
 4		158			131
 8		299			266
16		569			532
32		1131
64		2218

This doesn't look good, unless there is something wrong with my test (attached) or the cluster
settings.


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