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Tsz Wo (Nicholas), SZE commented on HDFS-512:
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Changing the key of the maps from block id and generation stamp to only block id sounds a
good idea. However, changing the Block.equal(..) method may not be correct. Conceptually,
block A is not equal to block B, given that they have the same id but distinct generation
stamps.
> 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: 0.21.0
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.21.0
>
> 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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