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Explorer
Posts: 16
Registered: ‎10-17-2014
Accepted Solution

New Disk in Data Node

Hello,

 

We have a 12 node cluster with 4 data drives in them each. We added 1 additional disk to each data node but are having a hard time getting data to be placed on these additional drives. For example:

 

node01 - 

/hdfs/01 - 1.4 TiB/1.8 TiB

/hdfs/02 - 1.5 TiB/1.8 TiB

/hdfs/03 - 1.5 TiB/1.8 TiB

/hdfs/04 - 1.5 TiB/1.8 TiB

/hdfs/05 - 18 GiB/1.8 TiB

 

node03 - 

/hdfs/01 - 1.5 TiB/1.8 TiB

/hdfs/02 - 1.5 TiB/1.8 TiB

/hdfs/03 - 1.5 TiB/1.8 TiB

/hdfs/04 - 1.5 TiB/1.8 TiB

/hdfs/05 - 181.9 GiB/1.8 TiB

 

We've run the rebalancer for a few weeks now. Would it be easier to just wipe one data node at a time and introduce it back into the cluster?

 

Thanks,

Eric

Highlighted
Posts: 266
Topics: 0
Kudos: 19
Solutions: 8
Registered: ‎08-19-2013

Re: New Disk in Data Node

The HDFS Balancer only balances blocks between DataNodes.   It does not to any balancing on individual DataNodes between drives.

 

You can set the DataNode Volume Choosing Policy (dfs.datanode.fsdataset.volume.choosing.policy) to Available Space (org.apache.hadoop.hdfs.server.datanode.fsdataset.AvailableSpaceVolumeChoosingPolicy).  This will cause the DataNodes to write new blocks to the drive with the most space available.   It does not affect blocks that have already been written.

 

For your question about wiping one datanode at a time, it would be better to decommission and then recommission a node.  With a replication factor of 3 you may perform this action on 2 nodes at a time.

 

 



David Enloe, Community Manager


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Explorer
Posts: 16
Registered: ‎10-17-2014

Re: New Disk in Data Node

Thanks for the quick reply. Much appreciated.
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