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https://issues.apache.org/jira/browse/HDFS-512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12739878#action_12739878
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Tsz Wo (Nicholas), SZE commented on HDFS-512:
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> I want to see at least one example where current the implementation (id+gs)
> of the block key is critical.
I did not say that I got a good example for using id+gs.
> (1) is too dangerous to get everything correct
Typo: it should be "(1) is too dangerous: it is very difficult to get
everything correct"
I mean (1) involves too much. I even have a hard time to list out all the
affected components in [my previous
comment|https://issues.apache.org/jira/browse/HDFS-512?focusedCommentId=12737395&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12737395].
BTW, I am not against (1) and I am not the assignee of this issue. Please go
ahead if you have fully considered other alternatives. I think the assignee
has the freedom to choose a solution.
> 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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