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New Disk in Data Node

avatar
Explorer

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

1 ACCEPTED SOLUTION

avatar
Community Manager

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 Wilder, Community Manager


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View solution in original post

2 REPLIES 2

avatar
Community Manager

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 Wilder, Community Manager


Was your question answered? Make sure to mark the answer as the accepted solution.
If you find a reply useful, say thanks by clicking on the thumbs up button.

Learn more about the Cloudera Community:

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avatar
Explorer
Thanks for the quick reply. Much appreciated.