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From "Walter Su (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8319) Erasure Coding: support decoding for stateful read
Date Thu, 04 Jun 2015 03:39:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14572056#comment-14572056
] 

Walter Su commented on HDFS-8319:
---------------------------------

{code}
void prepareParityChunk() {
  for (int i = dataBlkNum; i < dataBlkNum + parityBlkNum; i++) {
{code}
If pread starts from 4*cellSize (or stateful read skips to the pos), the first AlignedStripe
prepares data chunk\[4~5\]. If chunk\[4\] failed to read, we have to fetch parity chunk\[6~8\]
and data chunk\[0~1\], so we can decode chunk\[4\].
So the for loop should be cyclic and {{prepareParityChunk}} should renamed to {{prepareAdditionalChunk}}

> Erasure Coding: support decoding for stateful read
> --------------------------------------------------
>
>                 Key: HDFS-8319
>                 URL: https://issues.apache.org/jira/browse/HDFS-8319
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-8319.001.patch, HDFS-8319.002.patch, HDFS-8319.003.patch
>
>
> HDFS-7678 adds the decoding functionality for pread. This jira plans to add decoding
to stateful read.



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