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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7864) Erasure Coding: Update safemode calculation for striped blocks
Date Wed, 04 Mar 2015 22:33:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7864?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14347700#comment-14347700
] 

Jing Zhao commented on HDFS-7864:
---------------------------------

bq. I think "striped blocks" in this Jira's description actually denotes to "BlockGroup" in
"HDFSErasureCodingDesign-20150206.pdf" , right?

Yes, you're right. We should update the doc later for this.

bq. so a "BlockGroup" should be counted as 9 received blocks, right?

A block group (or a striped block) consists of 9 blocks in this case. But for safemode calculation,
I guess we can still count it as 1 block. This is because for a single striped block (suppose
it's m+k), we need a different logic to declare it's "safe" (as increase the safe amount by
1): the NN has received m blocks belonging to it from block reports (since we need m blocks
to recover all the data/parity blocks).

> Erasure Coding: Update safemode calculation for striped blocks
> --------------------------------------------------------------
>
>                 Key: HDFS-7864
>                 URL: https://issues.apache.org/jira/browse/HDFS-7864
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Jing Zhao
>            Assignee: GAO Rui
>
> We need to update the safemode calculation for striped blocks. Specifically, each striped
block now consists of multiple data/parity blocks stored in corresponding DataNodes. The current
code's calculation is thus inconsistent: each striped block is only counted as 1 expected
block, while each of its member block may increase the number of received blocks by 1.



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