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From Patrick Angeles <patr...@cloudera.com>
Subject Re: Hadoop Framework questions.
Date Wed, 02 Feb 2011 03:24:05 GMT
Hi, Raj.

Interesting analysis...

These numbers appear to be off. For example, 405s for mappers + 751s for
reducers = 1156s for all tasks. If you have 2000 map and reduce tasks, this
means each task is spending roughly 500ms to do actual work. That is a very
low number and seems impossible.

- P


On Wed, Feb 2, 2011 at 3:07 AM, Raj V <rajvish@yahoo.com> wrote:

>
> Hi
>
> I have been running some benchmarks with some hadoop jobs on different
> nodes and disk configurations to see what is a good configuration to get the
> optimum performance.
>
>
> Here are some results that I have. Using the hadoop job log, I added up the
> timings for each off the map task and reduce task and converted them to
> seconds by dividing by 1000. The job is terasort as provided in the
> examples.jar.
>
> Column 1 is the number of nodes in the cluster.
> Column 2 represents the sum of all the times map jobs for a task .  i.e.
> Sum over all TaskID's ( FINISH_TIME-START_TIME) where TASK_TYPE=Map.
> Column 3 the same calculation for all the reduce jobs. In all the cases all
> the tasks were sucessfully completed.
> Column 4 is the LAUNCH_TIME-FINISH_TIME for the Job. There is a SETUP_TASK
> and CLEANUP_TASK that take insignificant times.
> Column 5 is the proporation of time taken by the tasks= ( Col2+Col3)/Col4
>
> And I am assuming that Total_Time - (MAP_Time+REDUCE_Time)  is basically
> the framework time.
>
> Now looking at the data I see that thge framework is taking ~38%-68% of the
> timings
>
> Here are my questions.
>
> 1. Is this a problem with my setup or is this is the normal behaviour?
> 2. What can I do to reduce to the time taken for everything else?
> 3. Does this mean  that to get a reasonably efficient hadoop cluster (
> 10%-20% time for framework), do I need to get to a 1000 node cluster?
> 4. What is the normal "number" for the framework time ?
>
> I apologize for
>
> 1, Cross posting. I am using CDH3B3 but I don't think my questions are
> specific to CDH3B3.
> 2. Not having provided all the details of system,network, and disk
> configuration.
> 3. The different jobs have different disk configurations. Most of them are
> running about 2000 map and reduce jobs.
>
>
>      256 405.42 751.376 3483 0.332126328 256 411.574 711.841 3363
> 0.334051442 256 491.519 599.081 2955 0.369069374 512 491.034 1212.229 2989
> 0.56984376 512 471.421 947.025 2305 0.615377874 512 841 1932.633 4473
> 0.620083389
>

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