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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8230) Enable sync by default and disable append
Date Thu, 03 May 2012 17:00:49 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8230?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13267584#comment-13267584

Suresh Srinivas commented on HADOOP-8230:

bq. Would such an installation be using the sync call?
No from what I know.

>From what I understand, the intention of this change is to:
# Disable append, since 1.x has bugs in that implementation.
# Enable sync by default.

bq. Making sync actually work is a bug fix, it was a bug that we allowed people to call sync
and unlike append there wasn't a flag to enable it that was disabled by default. Better to
fix the default behavior (which allows you to sync).
The implementation earlier used dfs.supports.append to support both durable sync and append.
When this flag is off, whole bunch of code got turned off, related to sync functionality on
how the blocks are stored, block reports etc. Now with this change, this code can no longer
be turned off. I agree with enabling sync by default. However, for folks who chose not to
enable the related code and not impacted by it, we need to add a flag to turn off that functionality.
> Enable sync by default and disable append
> -----------------------------------------
>                 Key: HADOOP-8230
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8230
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 1.0.0
>            Reporter: Eli Collins
>            Assignee: Eli Collins
>             Fix For: 1.1.0
>         Attachments: hadoop-8230.txt
> Per HDFS-3120 for 1.x let's:
> - Always enable the sync path, which is currently only enabled if dfs.support.append
is set
> - Remove the dfs.support.append configuration option. We'll keep the code paths though
in case we ever fix append on branch-1, in which case we can add the config option back

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