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HADOOP - what is the default replication factor in HDFS?




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asked SRVMTrainings November 7, 2012 12:30 AM  

what is the default replication factor in HDFS?


           

2 Answers



 
answered By rajaniikanth   0  
Default replication is 3 and still its configrable
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answered By   0  

  The  default  hadoop comes with 3 replication factor. You can set the replication level individually for each file in HDFS. In addition to fault tolerance having replicas allow jobs that consume the same data to be run in parallel. Also if there are replicas of the data hadoop can attempt to run multiple copies of the same task and take which ever finishes first. This is useful if for some reason a box is being slow.

Most Hadoop administrators set the default replication factor for their files to be three. The main assumption here is that if you keep three copies of the data, your data is safe. this to be true in the big clusters that we manage and operate.
In addition to fault tolerance having replicas allow jobs that consume the same data to be run in parallel. Also if there are replicas of the data hadoop can attempt to run multiple copies of the same task and take which ever finishes first. This is useful if for some reason a box is being slow.

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