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HDFS, mail # dev - Re: What about over-replicated blocks in HDFS?

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Re: What about over-replicated blocks in HDFS?
Harsh J 2012-08-22, 08:35

NameNode takes care of over-replication situations, and you needn't
have to worry about over-replicated blocks or do anything manually.

On Wed, Aug 22, 2012 at 12:58 PM, Ajit Ratnaparkhi
> Hi,
> This is about case where HDFS has some data blocks which are
> over-replicated.
> Scenario is discussed below,
> If one of datanodes goes down, Namenode will see some blocks as under
> replicated and will start replication of under replicated blocks to bring
> their replication level back to expected. If after that datanode which was
> down comes up again without any data loss, at this time there will be blocks
> having more replication level than expected. Does namenode itself take care
> of removing extra blocks? or do we need to schedule balancer for that?
> -Ajit

Harsh J