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Posted to hdfs-issues@hadoop.apache.org by "Allen Wittenauer (JIRA)" <ji...@apache.org> on 2015/05/06 05:35:34 UTC
[jira] [Updated] (HDFS-4960) Unnecessary .meta seeks even when skip
checksum is true
[ https://issues.apache.org/jira/browse/HDFS-4960?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Allen Wittenauer updated HDFS-4960:
-----------------------------------
Labels: BB2015-05-TBR (was: )
> 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
> Labels: BB2015-05-TBR
> 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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