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https://issues.apache.org/jira/browse/HDFS-512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12739841#action_12739841
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Tsz Wo (Nicholas), SZE commented on HDFS-512:
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We have a concern that whether compareTo(..) has to be consistent with
equal(..). The answer is "strongly recommended but not required". See [the
Comparable API|http://java.sun.com/javase/6/docs/api/java/lang/Comparable.html].
bq. It is strongly recommended (though not required) that natural orderings be
consistent with equals. ...
> Set block id as the key to Block
> --------------------------------
>
> Key: HDFS-512
> URL: https://issues.apache.org/jira/browse/HDFS-512
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: Append Branch
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: Append Branch
>
> Attachments: blockKey.patch
>
>
> Currently the key to Block is block id + generation stamp. I would propose to
> change it to be only block id. This is based on the following properties of
> the dfs cluster:
> 1. On each datanode only one replica of block exists. Therefore there is only
> one generation of a block.
> 2. NameNode has only one entry for a block in its blocks map.
> With this change, search for a block/replica's meta information is easier
> since most of the time we know a block's id but may not know its generation
> stamp.
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