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Hadoop >> mail # user >> Issue:  Namenode is in safe mode

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Re: Issue: Namenode is in safe mode
what is your replication factor?
when you removed node A as datanode .. did you first mark it for
retirement? if you just removed it from service then the blocks from that
datanode are missing and namenode when starts up it checks for the blocks.
Unless it reaches its threshold value it will not let you write any more
data on your hdfs.

I will suggest to start datanode on A, then mark it for retirement so
namenode will move the blocks to new datanode and once it is done namenode
will retire that datanode.
On Wed, Mar 6, 2013 at 3:21 PM, AMARNATH, Balachandar <

> Hi,
> I have created a hadoop cluster with two nodes (A and B). ‘A’ act both as
> namenode and datanode, and ‘B’ act as datanode only. With this setup, I
> could store, read files. Now, I added one more datanode ‘C’ and relieved
> ‘A’ from datanode duty. This means, ‘A’ act only as namenode, and both B
> and C act as datanodes. Now, I tried to create a directory, it says
> ‘ org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create
> directory Name node is in safe mode’
> Can someone tell me why the namenode now is in safe mode?
> With thanks and regards
> Balachandar
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