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From "Liang Xie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6110) adding more slow action log in critical write path
Date Fri, 28 Mar 2014 06:17:16 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13950430#comment-13950430
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Liang Xie commented on HDFS-6110:
---------------------------------

Cool, with this, we could dig deeper once lots of threads stay at waitForAckedSeqno() or similar
function. With its help and other tools, i found one of our HBase cluster having write spike
issue, was cuased by Centos 6.3 's stable page write feature(In deed, per my understand, all
online HBase clusters which are care about latency, should never use RHEL/Centos 6.3 any more).

> adding more slow action log in critical write path
> --------------------------------------------------
>
>                 Key: HDFS-6110
>                 URL: https://issues.apache.org/jira/browse/HDFS-6110
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>    Affects Versions: 3.0.0, 2.3.0
>            Reporter: Liang Xie
>            Assignee: Liang Xie
>         Attachments: HDFS-6110-v2.txt, HDFS-6110.txt, HDFS-6110v3.txt
>
>
> After digging a HBase write spike issue caused by slow buffer io in our cluster, just
realize we'd better to add more abnormal latency warning log in write flow, such that if other
guys hit HLog sync spike, we could know more detail info from HDFS side at the same time.
> Patch will be uploaded soon.



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