Maybe your goal is to have a baseline for performance measurement? In that case, you might want to consider running only one taskTracker? You would have multiple tasks but running on only 1 machine. Also, you could make mappers run serially, by configuring only one map slot on your 1 node cluster.
Nevertheless I agree with Bertrand, this is not really a realistic use case (or maybe you can give us more clues). Julien 2013/2/26 Bertrand Dechoux <decho...@gmail.com> > http://wiki.apache.org/hadoop/HowManyMapsAndReduces > > It is possible to have a single mapper if the input is not splittable BUT > it is rarely seen as a feature. > One could ask why you want to use a platform for distributed computing for > a job that shouldn't be distributed. > > Regards > > Bertrand > > > > On Tue, Feb 26, 2013 at 12:09 PM, Arindam Choudhury < > arindamchoudhu...@gmail.com> wrote: > >> Hi all, >> >> I am trying to run terasort using one map and one reduce. so, I generated >> the input data using: >> >> hadoop jar hadoop-examples-1.0.4.jar teragen -Dmapred.map.tasks=1 >> -Dmapred.reduce.tasks=1 32000000 /user/hadoop/input32mb1map >> >> Then I launched the hadoop terasort job using: >> >> hadoop jar hadoop-examples-1.0.4.jar terasort -Dmapred.map.tasks=1 >> -Dmapred.reduce.tasks=1 /user/hadoop/input32mb1map /user/hadoop/output1 >> >> I thought it will run the job using 1 map and 1 reduce, but when inspect >> the job statistics I found: >> >> hadoop job -history /user/hadoop/output1 >> >> Task Summary >> ============================ >> Kind Total Successful Failed Killed StartTime FinishTime >> >> Setup 1 1 0 0 26-Feb-2013 10:57:47 26-Feb-2013 >> 10:57:55 (8sec) >> Map 24 24 0 0 26-Feb-2013 10:57:57 26-Feb-2013 >> 11:05:37 (7mins, 40sec) >> Reduce 1 1 0 0 26-Feb-2013 10:58:21 26-Feb-2013 >> 11:08:31 (10mins, 10sec) >> Cleanup 1 1 0 0 26-Feb-2013 11:08:32 26-Feb-2013 >> 11:08:36 (4sec) >> ============================ >> >> so, though I mentioned to launch one map tasks, there are 24 of them. >> >> How to solve this problem. How to tell hadoop to launch only one map. >> >> Thanks, >> > >
