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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4960) Unnecessary .meta seeks even when skip checksum is true
Date Sat, 02 May 2015 04:35:17 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14524739#comment-14524739
] 

Hadoop QA commented on HDFS-4960:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:red}-1{color} | patch |   0m  0s | The patch command could not apply the patch during
dryrun. |
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|| Subsystem || Report/Notes ||
| Patch URL | http://issues.apache.org/jira/secure/attachment/12591131/4960-trunk.patch |
| Optional Tests | javadoc javac unit findbugs checkstyle |
| git revision | trunk / f1a152c |
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/10583/console |


This message was automatically generated.

> Unnecessary .meta seeks even when skip checksum is true
> -------------------------------------------------------
>
>                 Key: HDFS-4960
>                 URL: https://issues.apache.org/jira/browse/HDFS-4960
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 3.0.0, 2.1.0-beta
>            Reporter: Varun Sharma
>            Assignee: Varun Sharma
>         Attachments: 4960-branch2.patch, 4960-trunk.patch
>
>
> While attempting to benchmark an HBase + Hadoop 2.0 setup on SSDs, we found unnecessary
seeks into .meta files, each seek was a 7 byte read at the head of the file - this attempts
to validate the version #. Since the client is requesting no-checksum, we should not be needing
to touch the .meta file at all.
> Since the purpose of skip checksum is to also avoid the performance penalty of the extra
seek, we should not be seeking into .meta if skip checksum is true



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