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https://issues.apache.org/jira/browse/HADOOP-1649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12518577
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Konstantin Shvachko commented on HADOOP-1649:
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+1
On 3: I mean that the performance gains are in single digits percentage-wise, 
so it is important to minimize memory costs,
that is I am agreeing you should file a new issue to deal with redundant data.


> 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, HADOOP-1649.patch, 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 cluster. 
> 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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