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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4111) readBlock in HFile.Reader not 64 KB, but 5~6MB
Date Wed, 20 Jul 2011 23:19:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13068707#comment-13068707
] 

stack commented on HBASE-4111:
------------------------------

Good on you Li Pi.

> readBlock in HFile.Reader not 64 KB, but 5~6MB
> ----------------------------------------------
>
>                 Key: HBASE-4111
>                 URL: https://issues.apache.org/jira/browse/HBASE-4111
>             Project: HBase
>          Issue Type: Bug
>          Components: io, regionserver
>            Reporter: mingjian
>            Assignee: Li Pi
>         Attachments: code and result.txt
>
>
>     We found a strange problem in our read test. 
>     It is a 5 nodes cluster.Four of our 5 regionservers set "hfile.block.cache.size"=0.4,
one of them is 0.1(we call it node A). When we random read from a 2TB data table we found
node A's network reached 100MB, and others are less than 10MB. So the read speed is low.
>     We set node A's "hfile.block.cache.size"=0.2, then all the nodes's network are 10MB,
that's right. To find why is this we debug with btrace and find "readBlock" in HFile.Reader
become abnormal.We know hbase read a block which is 64 KB from disks and put it into blockcache.
But when we set "hfile.block.cache.size"=0.1, it is not 64KB, it is 5~6MB one time after about
1 minute we restart hbase.
>     Why not 64 KB? The btrace code and results are in the attachments. 

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