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From "Marc-Olivier Fleury (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-4752) Major performance drop on slower machines
Date Tue, 02 Dec 2008 21:40:45 GMT
Major performance drop on slower machines
-----------------------------------------

                 Key: HADOOP-4752
                 URL: https://issues.apache.org/jira/browse/HADOOP-4752
             Project: Hadoop Core
          Issue Type: Bug
          Components: contrib/fuse-dfs
    Affects Versions: 0.18.2
            Reporter: Marc-Olivier Fleury


When running fuse_dfs on machines that have different CPU characteristics, I noticed that
the performance of fuse_dfs is very sensitive to the machine power. 

The command I used was simply a cat over a rather large amount of data stored on HDFS. Here
are the comparative times for the different types of machines:

Intel(R) Pentium(R) 4 CPU 2.40GHz :                                2 min 40 s 
Intel(R) Pentium(R) 4 CPU 3.06GHz:                                 1 min 50 s 
2 x Intel(R) Pentium(R) 4 CPU 3.00GHz:                           0 min 40 s 
2 x Intel(R) Xeon(TM) MP CPU 3.33GHz:                           0 min 28 s 
Intel(R) Core(TM)2 Quad CPU    Q6600  @ 2.40GHz      0 min 15 s

I tried to find other explanations for the drop in performance, such as network configuration,
or data locality, but the faster machines are the ones that are "further away" from the others
considering the network configuration, and that don't run datanodes.

top shows that the CPU usage of fuse_dfs is between 80-90% on the slower machines, and about
40% on the fastest one.

This leads me to the conclusion that fuse_dfs consumes a lot of CPU resources, much more than
expected.

Any help or insight concerning this issue will be greatly appreciated, since these difference
actually result in days of computations for a given job.

Thank you

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