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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1649) Performance regression with Block CRCs
Date Wed, 01 Aug 2007 22:09:53 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12517096

Raghu Angadi commented on HADOOP-1649:

bq. Digressing from this jira little bit.. Namenode does not need to track this information.
Datanode can report 'active write/reads' in its heartbeat and namenode can give preference
to the datanodes that have less active transactions in chooseTarget().

The load is already considered in DFS.

> Performance regression with Block CRCs
> --------------------------------------
>                 Key: HADOOP-1649
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1649
>             Project: Hadoop
>          Issue Type: Bug
>    Affects Versions: 0.14.0
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>            Priority: Blocker
>             Fix For: 0.14.0
>         Attachments: HADOOP-1649.patch
> Performance is noticeably affected by Block Level CRCs patch (HADOOP-1134). This is more
noticeable on writes (randomriter test etc). 
> With random writer, it takes 20-25% on small cluster (20 nodes) and many be 10% on larger
> There are a few differences in how data is written with 1134. As soon as I can reproduce
this, I think it will be easier to fix. 

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