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https://issues.apache.org/jira/browse/HDFS-7652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14289879#comment-14289879
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Zhe Zhang commented on HDFS-7652:
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This design question is mainly [discussed |
https://issues.apache.org/jira/browse/HDFS-7339?focusedCommentId=14289868&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14289868]
under HDFS-7339
Again, I really appreciate the in-depth thoughts! [~szetszwo] [~jingzhao]
> Process block reports for erasure coded blocks
> ----------------------------------------------
>
> Key: HDFS-7652
> URL: https://issues.apache.org/jira/browse/HDFS-7652
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
>
> HDFS-7339 adds support in NameNode for persisting block groups. For memory
> efficiency, erasure coded blocks under the striping layout are not stored in
> {{BlockManager#blocksMap}}. Instead, entire block groups are stored in
> {{BlockGroupManager#blockGroups}}. When a block report arrives from the
> DataNode, it should be processed under the block group that it belongs to.
> The following naming protocol is used to calculate the group of a given block:
> {code}
> * HDFS-EC introduces a hierarchical protocol to name blocks and groups:
> * Contiguous: {reserved block IDs | flag | block ID}
> * Striped: {reserved block IDs | flag | block group ID | index in group}
> *
> * Following n bits of reserved block IDs, The (n+1)th bit in an ID
> * distinguishes contiguous (0) and striped (1) blocks. For a striped block,
> * bits (n+2) to (64-m) represent the ID of its block group, while the last m
> * bits represent its index of the group. The value m is determined by the
> * maximum number of blocks in a group (MAX_BLOCKS_IN_GROUP).
> {code}
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