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https://issues.apache.org/jira/browse/HADOOP-2148?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Konstantin Shvachko updated HADOOP-2148:
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Description:
FSDataset.getBlockFile() first verifies that the block is valid and then
returns the file name corresponding to the block.
Doing that it performs the data-node blockMap lookup twice. Only one lookup is
needed here.
This is important since the data-node blockMap is big.
Another observation is that data-nodes do not need the blockMap at all. File
names can be derived from the block IDs,
there is no need to hold Block to File mapping in memory.
was:
FSDataset.getBlockFile() first verifies that the block is valid and then
returns the file name corresponding to the block.
Doing that it performs the data-node blockMap lookup twice. Only one lookup is
needed here.
This is important since the data-node blockMap is big.
> Inefficient FSDataset.getBlockFile()
> ------------------------------------
>
> Key: HADOOP-2148
> URL: https://issues.apache.org/jira/browse/HADOOP-2148
> Project: Hadoop
> Issue Type: Improvement
> Affects Versions: 0.14.0
> Reporter: Konstantin Shvachko
> Fix For: 0.16.0
>
>
> FSDataset.getBlockFile() first verifies that the block is valid and then
> returns the file name corresponding to the block.
> Doing that it performs the data-node blockMap lookup twice. Only one lookup
> is needed here.
> This is important since the data-node blockMap is big.
> Another observation is that data-nodes do not need the blockMap at all. File
> names can be derived from the block IDs,
> there is no need to hold Block to File mapping in memory.
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