Home Forums HDFS Adding new data volumes

This topic contains 1 reply, has 2 voices, and was last updated by  tedr 1 year, 4 months ago.

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  • #25150

    Hi,

    I’m trying to add some disk space to one of our nodes. We currently have a heterogeneous setup with one data directory configured on each node. I was able to aquire some extra disks for one of the nodes, arranged in a JBOD format. I’m not able to get any for our other nodes at the moment.

    As I understand it, Hadoop should support heterogeneous disk layouts. I understand it’s not optimal, but it’s the best I can do for now.

    The official Hadoop documentation for version 1.1.2 states that the variable dfs.data.dir “Determines where on the local filesystem an DFS data node should store its blocks. If this is a comma-delimited list of directories, then data will be stored in all named directories, typically on different devices. Directories that do not exist are ignored.”

    Since diretories that don’t exist should be ignored, I decided to change dfs.data.dir to the existing directory plus the four new ones, plus five that don’t exist yet for future expansion. I did this through the REST API since it’s not possible to change via Ambari directly. I also changed the “DataNode volumes failure toleration” to 9 so that I wouldn’t get startup errors.

    The problem is that now I get the following error on all the datanodes, which fail to start:

    2013-05-10 13:48:57,650 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: org.apache.hadoop.util.DiskChecker$DiskErrorException: Invalid value for validVolsRequired : -8 , Current valid volumes: 1
    at org.apache.hadoop.hdfs.server.datanode.FSDataset.(FSDataset.java:982)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:407)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.(DataNode.java:313)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1674)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1613)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1631)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1757)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1774)

    Is it even possible to add additional data volumes to a single node? What would be the recommended solution to this, assuming that I cannot acquire extra hard drives for some time?

    Thank you,
    John

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  • #26433

    tedr
    Member

    Hi John,

    Unfortunately, Ambari does not currently support differing volumes on data nodes, this feature is planeed for a future release.

    Thanks,
    Ted.

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