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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-971) Improve name node performance by adding a hostname to datanodes map
Date Wed, 14 Mar 2007 19:15:09 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12480877
] 

dhruba borthakur commented on HADOOP-971:
-----------------------------------------

I saw getDatanodeByHost() consumes appreciable amount of CPU on a 1800 node cluster. 

> Improve name node performance by adding a hostname to datanodes map
> -------------------------------------------------------------------
>
>                 Key: HADOOP-971
>                 URL: https://issues.apache.org/jira/browse/HADOOP-971
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.11.0
>            Reporter: Hairong Kuang
>         Assigned To: Hairong Kuang
>
> A name node currently maintains a datanode map which maps a storage id to a dataNodeDescriptor.
When the name node needs to get a datanodeDescriptor by its name (hostname:port#) or by its
host name, it has to iterate through the data node set, which is very inefficent. I'd like
to add an additional map that maps a host name to an array list of DatanodeDescriptors that
contains all the data nodes running on the host. Since most of time a node runs only one data
node, the intial size of the array list is set to be 1.

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