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https://issues.apache.org/jira/browse/HDFS-7354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14379271#comment-14379271
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Tsz Wo Nicholas Sze commented on HDFS-7354:
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> Parity blocks still need special treatment though, because they should be
> recovered with lower priority than data blocks. ...
I think the priority should be depended on the number of missing blocks since
all the missing blocks in a block group can be reconstructed at the same time.
For (6,3)-Reed-Solomon, the priority should be:
- 1-missing: lowest priority (or do not reconstruct it at all)
- 2-missing: low priority (the same as 1-missing in 3-replication)
- 3-missing: high priority (data loss if one more block is missing.)
> Support parity blocks in block management
> -----------------------------------------
>
> Key: HDFS-7354
> URL: https://issues.apache.org/jira/browse/HDFS-7354
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
>
> Parity blocks are not accessed during normal I/O operations. They should
> therefore be treated with lower priority in the block recovery framework.
> This JIRA tracks this effort as well as other special treatments which might
> be needed for parity blocks.
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