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Date: Mon, 25 Jun 2012 16:45:45 +0000 (UTC)
From: "Aaron T. Myers (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-3475) Make the replication monitor
 multipliers configurable
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    [ https://issues.apache.org/jira/browse/HDFS-3475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13400599#comment-13400599 ] 

Aaron T. Myers commented on HDFS-3475:
--------------------------------------

One small comment: I think you should add some info to the hdfs-default.xml description for "{{dfs.namenode.invalidate.work.pct.per.iteration}}" saying that the value should be between 0-100, or whatever's appropriate. For that matter, since this is a brand new config, you might want to change it to be in the range 0 - 1.0, which I think is a more common way in the Hadoop code base to represent percentages.

Other than that the patch looks good. +1 pending a fix for the above and an explanation of the two test failures.
                
> Make the replication monitor multipliers configurable
> -----------------------------------------------------
>
>                 Key: HDFS-3475
>                 URL: https://issues.apache.org/jira/browse/HDFS-3475
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.0.0-alpha
>            Reporter: Harsh J
>            Assignee: Harsh J
>            Priority: Trivial
>         Attachments: HDFS-3475.patch, HDFS-3475.patch
>
>
> BlockManager currently hardcodes the following two constants:
> {code}
> private static final int INVALIDATE_WORK_PCT_PER_ITERATION = 32;
> private static final int REPLICATION_WORK_MULTIPLIER_PER_ITERATION = 2;
> {code}
> These are used to throttle/limit the amount of deletion and replication-to-other-DN work done per heartbeat interval of a live DN.
> Not many have had reasons to want these changed so far but there have been a few requests I've faced over the past year from a variety of clusters I've helped maintain. I think with the improvements in disks and network thats already started to be rolled out in production environments out there, changing these may start making sense to some.
> Lets at least make it advanced-configurable with proper docs that warn adequately, with the defaults being what they are today. With hardcodes, it comes down to a recompile for admins, which is not something they may like.
> Please let me know your thoughts.

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