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From adarsh deshratnam <adarsh.deshrat...@gmail.com>
Subject Re: Query regarding the replication factor in hadoop
Date Fri, 19 Sep 2014 12:36:39 GMT
1. *How hadoop will take care of balancing of replicas as the required
replicas are 3 , but we have only 2 data nodes up and running.*

*Ans:* As here the replication factor is three. The data block will be
replicated three time within 2 nodes. Block replication is random.

*2. What happens when we try to write new  data into hdfs at this point of
time ? whether the write would be successful with only 2 data nodes and
replication factor 3 or it returns any error message?*
*Ans:*It will write successfully.


For further info please refer below link:
http://hadoop.apache.org/docs/r1.2.1/hdfs_design.html


Thanks,
Adarsh D

On Fri, Sep 19, 2014 at 5:46 PM, Raghavendra Chandra <
raghavchandra.learning@gmail.com> wrote:

> Hi All,
>
> I have one very basic query regarding the replication factor in HDFS.
>
> Scenario:
>
> I have 4 node cluster : 3 data nodes and 1 master node.
>
> The replication factor is 3. So ideally each data node would  get one
> replica .
>
> Assume that meanwhile one of the data node went down.
>
> so ideally we will be having 2 data nodes.
>
> Queries:
>
> 1. How hadoop will take care of balancing of replicas as the required
> replicas are 3 , but we have only 2 data nodes up and running.
>
> 2. What happens when we try to write new  data into hdfs at this point of
> time ? whether the write would be successful with only 2 data nodes and
> replication factor 3 or it returns any error message?
>
>
> These queries might be simple, but it would be really helpful if some one
> can answer.
>
> Thanks and regards,
> Raghav Chandra
>
>

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