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https://issues.apache.org/jira/browse/HDFS-6658?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daryn Sharp updated HDFS-6658:
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Attachment: New primative indexes.jpg
Old triplets.jpg
Excuse my bad whiteboard drawing skills. These pictures attempt to illustrate
the triplets vs the data structures. It shows a 3-block file with repl factor
2 that is stored on 2 nodes. I started trying to diagram a 3-repl factor
picture with proper block placement on multiple nodes but it was spaghetti for
the triplets. My whiteboard isn't that big.
Everything is a reference in the triplets pic. The new pic is based on
primitive indexes. The design I recently posted goes into more detail on the
indexing.
> Namenode memory optimization - Block replicas list
> ---------------------------------------------------
>
> Key: HDFS-6658
> URL: https://issues.apache.org/jira/browse/HDFS-6658
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 2.4.1
> Reporter: Amir Langer
> Assignee: Daryn Sharp
> Attachments: BlockListOptimizationComparison.xlsx, BlocksMap
> redesign.pdf, HDFS-6658.patch, HDFS-6658.patch, HDFS-6658.patch, Namenode
> Memory Optimizations - Block replicas list.docx, New primative indexes.jpg,
> Old triplets.jpg
>
>
> Part of the memory consumed by every BlockInfo object in the Namenode is a
> linked list of block references for every DatanodeStorageInfo (called
> "triplets").
> We propose to change the way we store the list in memory.
> Using primitive integer indexes instead of object references will reduce the
> memory needed for every block replica (when compressed oops is disabled) and
> in our new design the list overhead will be per DatanodeStorageInfo and not
> per block replica.
> see attached design doc. for details and evaluation results.
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