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From Joey Echeverria <j...@cloudera.com>
Subject Re: What does hdfs balancer do after adding more disks to existing datanode.
Date Tue, 22 Nov 2011 11:55:56 GMT
The balancer only balances between datanodes. This means the new
drives won't get used until you start writing new data to them. If you
want to balance the drives on a node, you need to

1) copy a bunch of block files from the old drives to the new drives
2) shutdown the datanode
3) delete the old block files
4) configure the datanode to see the new drives
5) start the datanode


On Tue, Nov 22, 2011 at 6:43 AM, Ajit Ratnaparkhi
<ajit.ratnaparkhi@gmail.com> wrote:
> Hi,
> If I add additional disks to existing datanode (assume existing datanode has
> 7 1TB disk which are already 80% full and then I add two new 2TB disks 0%
> full) and then run balancer, does balancer balance data in a datanode? ie.
> Will it move data from existing disks to newly added disks such that all
> disks are approx equally full ?
> thanks,
> Ajit.

Joseph Echeverria
Cloudera, Inc.

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