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Date: Sun, 7 Jul 2013 16:59:48 +0000 (UTC)
From: "Varun Sharma (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12656521.1373214921043.8804.1373216388722@arcas>
In-Reply-To: <JIRA.12656521.1373214921043@arcas>
References: <JIRA.12656521.1373214921043@arcas>
Subject: [jira] [Updated] (HDFS-4960) Unnecessary .meta seeks even when skip
 checksum is true
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     [ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Varun Sharma updated HDFS-4960:
-------------------------------

    Issue Type: Bug  (was: Improvement)
    
> 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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