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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-898) Sequential generation of block ids
Date Fri, 15 Jan 2010 22:54:54 GMT

    [ https://issues.apache.org/jira/browse/HDFS-898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12800978#action_12800978
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dhruba borthakur commented on HDFS-898:
---------------------------------------

>The prehistoric block problem is still relevant, since the name-node's block-map keys
blocks by their ids, 
> see HDFS-512. Although now there is less chance to corrupt a block with a stale replica,

> because stale replicas will have older generation stamps.

Can you pl explain why this is so? I thought that the list of blocks that hang off a Inode
still has the generation stamp in it. If a datanode sends a block report with a pre-historic
blockId, it can be detected at the NN because the genstamp of that block will not match the
generation stamp of the blocks that hang off the inode.

> Sequential generation of block ids
> ----------------------------------
>
>                 Key: HDFS-898
>                 URL: https://issues.apache.org/jira/browse/HDFS-898
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.20.1
>            Reporter: Konstantin Shvachko
>            Assignee: Konstantin Shvachko
>             Fix For: 0.22.0
>
>
> This is a proposal to replace random generation of block ids with a sequential generator
in order to avoid block id reuse in the future.

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