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https://issues.apache.org/jira/browse/HDFS-512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12739831#action_12739831
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Tsz Wo (Nicholas), SZE commented on HDFS-512:
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I forgot to say that my preference would be (2) > (3) > (1) because
- (1) is too dangerous to get everything correct and is an incompatible change;
and
- (3) seems requiring more code changes than (2).
> 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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